BigTree SKR Pro V1.1 board support (#14523)

Marlin/src/HAL/HAL_STM32/HAL.h

Marlin/src/core/boards.h

Marlin/src/pins/pins.h

Marlin/src/pins/pins_BIGTREE_SKR_PRO_V1.1.h

buildroot/share/PlatformIO/boards/BigTree_SKR_Pro.json

buildroot/share/PlatformIO/scripts/generic_create_variant.py

...IO/variants/BIGTREE_GENERIC_STM32F407_5X/PeripheralPins.c

...ormIO/variants/BIGTREE_GENERIC_STM32F407_5X/PinNamesVar.h

...tformIO/variants/BIGTREE_GENERIC_STM32F407_5X/ldscript.ld

...ariants/BIGTREE_GENERIC_STM32F407_5X/stm32f4xx_hal_conf.h

...tformIO/variants/BIGTREE_GENERIC_STM32F407_5X/variant.cpp

...latformIO/variants/BIGTREE_GENERIC_STM32F407_5X/variant.h

platformio.ini