DISCO_L475VG_IOT01A: Add comment to inform that GPIO pinmap is for testing only

Author: mprse

targets/TARGET_STM/TARGET_STM32L4/TARGET_STM32L475xG/TARGET_DISCO_L475VG_IOT01A/PeripheralPinMaps.h

@@ -53,7 +53,7 @@
 #include <mstd_cstddef>
 
 //*** GPIO ***
-
+// Pinmap used for FPGA GPIO testing only
 MSTD_CONSTEXPR_OBJ_11 PinMap PinMap_GPIO[] = {
     {PA_0, GPIO_X, 0},
     {PA_1, GPIO_X, 0},