The retu watchdog calls into the respective mfd driver, but fails to
link if that is diabled:
drivers/watchdog/built-in.o: In function `retu_wdt_set_timeout':
ziirave_wdt.c:(.text+0x8c88): undefined reference to `retu_write'
ziirave_wdt.c:(.text+0x8c88): relocation truncated to fit: R_AARCH64_CALL26 against undefined symbol `retu_write'
drivers/watchdog/built-in.o: In function `retu_wdt_start':
ziirave_wdt.c:(.text+0x8cc8): undefined reference to `retu_write'
ziirave_wdt.c:(.text+0x8cc8): relocation truncated to fit: R_AARCH64_CALL26 against undefined symbol `retu_write'