Shutdown to VBAT mode Stm32mp157c

Followed this to enable complete shutdown on ST DK2 board:

However, similar change to stm32mp157c-odyssey.dtsi file in tf-a/fdts/ causes a watchdog timeout when “shutdown -h 0” is executed in linux.

root@edge:~# shutdown -h 0
Shutdown scheduled for Sun 2020-09-20 10:50:03 UTC, use 'shutdown -c' to cancel.
root@edge:~# [  369.454639] watchdog: watchdog0: watchdog did not stop!
[  369.705694] Default copro already stopped
[  369.757686] reboot: Power down
INFO:    PSCI Power Domain Map:
INFO:      Domain Node : Level 1, parent_node -1, State ON (0x0)
INFO:      Domain Node : Level 0, parent_node 0, State ON (0x0)
INFO:      CPU Node : MPID 0x0, parent_node 0, State ON (0x0)
INFO:      CPU Node : MPID 0x1, parent_node 0, State ON (0x0)
NOTICE:  Model: STMicroelectronics STM32MP157C-DK2 Discovery Board
INFO:    Reset reason (0x214):
INFO:      IWDG2 Reset (rst_iwdg2)
INFO:    PMIC version = 0x21
INFO:    FCONF: Reading TB_FW firmware configuration file from: 0x2ffe3000
INFO:    FCONF: Reading firmware configuration information for: stm32mp_io
INFO:    Using SDMMC
INFO:      Instance 1