Update of BT power up sequences to remove redundant delay (500ms) in BT_POWER operation during HCIDrive initialization.

Current BT_POWER sequence:
1. BT_POWER=0  ( from CyH4TransportDriver::initialize)
2. delay 1ms   ( from CyH4TransportDriver::initialize)
3. BT_POWER=1  ( from CyH4TransportDriver::initialize)
4. delay 500ms (from HCIDriver::do_initialize)
5. BT_POWER=1  (from HCIDriver::do_initialize)
6. delay 500ms (from HCIDriver::do_initialize)

updates:
1. remove 4) and 5)
2. keep all BT_POWER operations in one place. The best logic place is CyH4TransportDriver::initialize.

So finally the BT_POWER sequences should looks like:
1. BT_POWER=0  ( from CyH4TransportDriver::initialize)
2. delay 1ms   ( from CyH4TransportDriver::initialize)
3. BT_POWER=1  ( from CyH4TransportDriver::initialize)
4. delay 500ms ( from CyH4TransportDriver::initialize)

connectivity/drivers/ble/FEATURE_BLE/COMPONENT_CYW43XXX/CyH4TransportDriver.cpp

@@ -29,6 +29,17 @@
 #include "rtos/ThisThread.h"
 #include <chrono>
 
+// BT settling time after power on
+#if !defined (CY_BT_POWER_ON_SETTLING_TIME)
+    #define CY_BT_POWER_ON_SETTLING_TIME                    (500ms)
+#endif /* !defined (CY_BT_POWER_ON_SETTLING_TIME) */
+
+// Power on reset time 
+#if !defined (CY_BT_POWER_ON_RESET_TIME)
+    #define CY_BT_POWER_ON_RESET_TIME                       (1ms)      
+#endif /* !defined (CY_BT_POWER_ON_RESET_TIME) */
+
+
 namespace ble {
 namespace vendor {
 namespace cypress_ble {
@@ -153,8 +164,9 @@ void CyH4TransportDriver::initialize()
     bt_host_wake_active = true;
     sleep_manager_lock_deep_sleep();
 
+    // Keep the bt_power line in the low level to ensure that the device resets.
     bt_power = 0;
-    rtos::ThisThread::sleep_for(1ms);
+    rtos::ThisThread::sleep_for(CY_BT_POWER_ON_RESET_TIME);
 
 #if defined(CYW43XXX_UNBUFFERED_UART)
     uart.baud(DEF_BT_BAUD_RATE);
@@ -186,7 +198,9 @@ void CyH4TransportDriver::initialize()
     cyhal_uart_enable_event(&uart, CYHAL_UART_IRQ_RX_NOT_EMPTY, CYHAL_ISR_PRIORITY_DEFAULT, true);
 #endif
 
+    // Power up BT
     bt_power = 1;
+    rtos::ThisThread::sleep_for(CY_BT_POWER_ON_SETTLING_TIME);
 
 #if (defined(MBED_TICKLESS) && DEVICE_SLEEP && DEVICE_LPTICKER)
     if (bt_host_wake_name != NC) {
@@ -229,6 +243,7 @@ void CyH4TransportDriver::terminate()
 
     deassert_bt_dev_wake();
 
+    // Power down BT
     bt_power = 0; //BT_POWER is an output, should not be freed only set inactive
 
 #if defined(CYW43XXX_UNBUFFERED_UART)

connectivity/drivers/ble/FEATURE_BLE/COMPONENT_CYW43XXX/HCIDriver.cpp

@@ -101,9 +101,6 @@ public:
 
     virtual void do_initialize()
     {
-        rtos::ThisThread::sleep_for(500ms);
-        bt_power = 1;
-        rtos::ThisThread::sleep_for(500ms);
     }
 
     virtual void do_terminate() { }