Corrected PPP thread stack sizes and network interface

Corrected PPP thread stack size for RZ_A1_EMAC, CYW943012P6EVB_01,
CY8CPROTO_062_4343W, CY8CKIT_062_WIFI_BT and CY8CKIT_062S2_43012
that have special configuration for PPP thread size. Removed
pppInterface() helper call from network interface. It causes binary
compatibility break with precompiled network interface classes. Call
is helper function to check network interface type in case it is
unknown, and is not mandatory or used with PPP.

features/lwipstack/mbed_lib.json

@@ -168,7 +168,6 @@
         "RZ_A1_EMAC": {
             "tcpip-thread-stacksize": 1328,
             "default-thread-stacksize": 640,
-            "ppp-thread-stacksize": 896,
             "memp-num-tcp-seg": 32,
             "tcp-mss": 1440,
             "tcp-snd-buf": "(8 * TCP_MSS)",
@@ -179,7 +178,6 @@
         "CYW943012P6EVB_01": {
             "tcpip-thread-stacksize": 8192,
             "default-thread-stacksize": 640,
-            "ppp-thread-stacksize": 896,
             "memp-num-tcp-seg": 24,
             "tcp-socket-max": 10,
             "udp-socket-max":10,
@@ -193,7 +191,6 @@
         "CY8CPROTO_062_4343W": {
             "tcpip-thread-stacksize": 8192,
             "default-thread-stacksize": 640,
-            "ppp-thread-stacksize": 896,
             "memp-num-tcp-seg": 24,
             "tcp-socket-max": 10,
             "udp-socket-max":10,
@@ -207,7 +204,6 @@
         "CY8CKIT_062_WIFI_BT": {
             "tcpip-thread-stacksize": 8192,
             "default-thread-stacksize": 640,
-            "ppp-thread-stacksize": 896,
             "memp-num-tcp-seg": 48,
             "tcp-socket-max": 10,
             "udp-socket-max":10,
@@ -221,7 +217,6 @@
         "CY8CKIT_062S2_43012": {
            "tcpip-thread-stacksize": 8192,
            "default-thread-stacksize": 640,
-           "ppp-thread-stacksize": 896,
            "memp-num-tcp-seg": 24,
            "tcp-socket-max": 10,
            "udp-socket-max":10,

features/netsocket/NetworkInterface.h

@@ -339,14 +339,6 @@ public:
         return 0;
     }
 
-    /** Return pointer to a PPPInterface.
-     * @return Pointer to requested interface type or NULL if this class doesn't implement the interface.
-     */
-    virtual PPPInterface *pppInterface()
-    {
-        return 0;
-    }
-
     /** Return pointer to a CellularInterface.
      * @return Pointer to requested interface type or NULL if this class doesn't implement the interface.
      * @deprecated CellularBase migrated to CellularInterface - use cellularInterface()

features/netsocket/ppp/mbed_lib.json

@@ -34,7 +34,19 @@
     },
     "target_overrides": {
         "RZ_A1_EMAC": {
-            "ppp-thread-stacksize": 896
+            "thread-stacksize": 896
+        },
+        "CYW943012P6EVB_01": {
+            "thread-stacksize": 896
+        },
+        "CY8CPROTO_062_4343W": {
+            "thread-stacksize": 896
+        },
+        "CY8CKIT_062_WIFI_BT": {
+            "thread-stacksize": 896
+        },
+        "CY8CKIT_062S2_43012": {
+            "thread-stacksize": 896
         }
     }
 }