stm32/boards/NUCLEO_H743ZI: Add config options to support mboot.

ports/stm32/boards/NUCLEO_H743ZI/mpconfigboard.mk

+USE_MBOOT ?= 0
+
+# MCU settings
 MCU_SERIES = h7
 CMSIS_MCU = STM32H743xx
 MICROPY_FLOAT_IMPL = double
 AF_FILE = boards/stm32h743_af.csv
+
+ifeq ($(USE_MBOOT),1)
+# When using Mboot all the text goes together after the filesystem
+LD_FILES = boards/stm32h743.ld boards/common_blifs.ld
+TEXT0_ADDR = 0x08040000
+else
+# When not using Mboot the ISR text goes first, then the rest after the filesystem
 LD_FILES = boards/stm32h743.ld boards/common_ifs.ld
 TEXT0_ADDR = 0x08000000
 TEXT1_ADDR = 0x08040000
+endif