Support for STM32H503 MCU - review changes

Implemented changes suggested in the review:
- restored original name of SystemClock_Config() function
- some GPIO clocks are only enabled if macros are defined
- moved GPIO clocks init back to family.c

src/portable/st/stm32_fsdev/dcd_stm32_fsdev.h

@@ -116,7 +116,7 @@
   #include "stm32h5xx.h"
   #define FSDEV_BUS_32BIT
 
-  #ifdef STM32H503xx
+  #if !defined(USB_DRD_BASE) && defined(USB_DRD_FS_BASE)
   #define USB_DRD_BASE USB_DRD_FS_BASE
   #endif