stmhal: Include mpconfig.h before all other includes.

stmhal/boards/stm32f4xx-prefix.c

stmhal/bufhelper.c

stmhal/diskio.c

stmhal/gccollect.c

stmhal/import.c

stmhal/lexerfatfs.c

stmhal/main.c

stmhal/pendsv.c

stmhal/pin_named_pins.c

stmhal/printf.c

stmhal/pybstdio.c

stmhal/readline.c

stmhal/rng.c

stmhal/rtc.c

stmhal/sdcard.c

stmhal/stm32f4xx_hal_msp.c

stmhal/stm32f4xx_it.c

stmhal/storage.c

stmhal/systick.c

stmhal/usrsw.c