[STM32F4] SPI Peripheral pin - allow SPI3 to be used

Let's swap default PA_4 pin mapping to SPI_3 otherwise SPI3 cannot be used

Author: Laurent MEUNIER

targets/TARGET_STM/TARGET_STM32F4/TARGET_ELMO_F411RE/PeripheralPins.c

@@ -196,8 +196,8 @@ const PinMap PinMap_SPI_SCLK[] = {
 };
 
 const PinMap PinMap_SPI_SSEL[] = {
-    {PA_4,  SPI_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_NOPULL, GPIO_AF5_SPI1)},
-//  {PA_4,  SPI_3, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_NOPULL, GPIO_AF6_SPI3)},
+   //  {PA_4,  SPI_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_NOPULL, GPIO_AF5_SPI1)},
+    {PA_4,  SPI_3, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_NOPULL, GPIO_AF6_SPI3)},
     {PA_15, SPI_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_NOPULL, GPIO_AF5_SPI1)},
 //  {PA_15, SPI_3, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_NOPULL, GPIO_AF6_SPI3)},
     {PB_1,  SPI_5, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF6_SPI5)},

targets/TARGET_STM/TARGET_STM32F4/TARGET_NUCLEO_F411RE/PeripheralPins.c

@@ -208,8 +208,8 @@ const PinMap PinMap_SPI_SCLK[] = {
 };
 
 const PinMap PinMap_SPI_SSEL[] = {
-    {PA_4,  SPI_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_NOPULL, GPIO_AF5_SPI1)},
-//  {PA_4,  SPI_3, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_NOPULL, GPIO_AF6_SPI3)},
+//    {PA_4,  SPI_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_NOPULL, GPIO_AF5_SPI1)},
+  {PA_4,  SPI_3, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_NOPULL, GPIO_AF6_SPI3)},
     {PA_15, SPI_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_NOPULL, GPIO_AF5_SPI1)},
 //  {PA_15, SPI_3, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_NOPULL, GPIO_AF6_SPI3)},
     {PB_1,  SPI_5, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF6_SPI5)},