board: st: stm32mp25: support dynamic A/B bank bootup

board: st: stm32mp25: support dynamic A/B bank bootup

Enable automatic detection of the active A/B bank by retrieving
partition GUIDs from FWU metadata.

This ensures the system correctly identifies the bootable partitions
even in multi-bank scenarios, falling back to a standard bootable flag
scan if the UUIDs are missing.

To enable A/B bank bootup on stm32mp25 boards, add the following Kconfig
options to the stm32mp25_defconfig:

 CONFIG_FWU_MULTI_BANK_UPDATE=y
 CONFIG_FWU_MDATA=y
 CONFIG_FWU_NUM_BANKS=2
 CONFIG_FWU_NUM_IMAGES_PER_BANK=3
 CONFIG_CMD_FWU_METADATA=y
 CONFIG_FWU_MDATA_V2=y

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>