USBHost: Silence GCC warnings in USBHost.cpp

There are a few warnings thrown by GCC for this source file that I have
attempted to correct.  I would definitely appreciate feedback from
others on these changes:
* USBHost::usb_process() would attempt to write past the end of the
  deviceInited[] array in the following code snippet:
    if (i == MAX_DEVICE_CONNECTED) {
        USB_ERR("Too many device connected!!\r\n");
        deviceInited[i] = false;
  The i variable is guaranteed to index 1 item past then end of this
  array since it only contains MAX_DEVICE_CONNECTED elements.  I have
  removed the line which sets deviceInited[i] to false.  Two questions
  result though:
    1) What was the intent of this line of code and is it Ok that I
       just removed it or should it be replaced with something else?
    2) I see no where else that elements in the deviceInited array are
       set to false except when all are set to false in the usbThread()
       method.  Should there be code in DEVICE_DISCONNECTED_EVENT to
       do this as well?
* USBHost::transferCompleted(volatile uint32_t addr) was comparing addr
  to NULL, which is of pointer type.  GCC issues a warning on this
  since the types are different (void* being compared to uint32_t).  I
  switched it to just compare with 0 instead.
* There is a switch statement in USBHost::unqueueEndpoint() which
  is conditional on a ENDPOINT_TYPE enumeration but doesn't contain
  cases for all values in the enumeration.  I just added a default
  case to simply break on other values to silence this GCC warning and
  allow the code to continue working as it did before.  Is it Ok that
  this particular piece of code only handles these two particular
  cases?
* USBHost::fillControlBuf() was generating a warning about possible
  alignment issues when accessing the setupPacket byte array as 16-bit
  half words instead.  I changed the casting to silence the warnings
  and modified the declaration of the setupPacket field to make sure
  that it is at least 2-byte aligned for these 16-bit accesses.

libraries/USBHost/USBHost/USBHost.cpp

@@ -96,7 +96,6 @@ void USBHost::usb_process() {
                     
                     if (i == MAX_DEVICE_CONNECTED) {
                         USB_ERR("Too many device connected!!\r\n");
-                        deviceInited[i] = false;
                         usb_mutex.unlock();
                         continue;
                     }
@@ -287,7 +286,7 @@ void USBHost::transferCompleted(volatile uint32_t addr)
 {
     uint8_t state;
 
-    if(addr == NULL)
+    if(addr == 0)
         return;
 
     volatile HCTD* tdList = NULL;
@@ -482,6 +481,8 @@ void USBHost::unqueueEndpoint(USBEndpoint * ep)
                         case INTERRUPT_ENDPOINT:
                             tailInterruptEndpoint = prec;
                             break;
+                        default:
+                            break;
                     }
                 }
                 current->setState(USB_TYPE_FREE);
@@ -1158,7 +1159,8 @@ void USBHost::fillControlBuf(uint8_t requestType, uint8_t request, uint16_t valu
     setupPacket[0] = requestType;
     setupPacket[1] = request;
     //We are in LE so it's fine
-    *((uint16_t*)&setupPacket[2]) = value;
-    *((uint16_t*)&setupPacket[4]) = index;
-    *((uint16_t*)&setupPacket[6]) = (uint32_t) len;
+    uint16_t* setupPacketHalfWords = (uint16_t*)setupPacket;
+    setupPacketHalfWords[1] = value;
+    setupPacketHalfWords[2] = index;
+    setupPacketHalfWords[3] = (uint32_t) len;
 }

libraries/USBHost/USBHost/USBHost.h

@@ -252,7 +252,7 @@ private:
 #endif
 
     // to store a setup packet
-    uint8_t  setupPacket[8];
+    __attribute__((aligned(2))) uint8_t  setupPacket[8];
     
     typedef struct {
         uint8_t event_id;