The kempld watchdog driver requires the respective MFD driver:
drivers/watchdog/built-in.o: In function `kempld_wdt_probe':
kempld_wdt.c:(.text+0x5c78): undefined reference to `kempld_get_mutex'
kempld_wdt.c:(.text+0x5c84): undefined reference to `kempld_read8'
kempld_wdt.c:(.text+0x5c8e): undefined reference to `kempld_release_mutex'
kempld_wdt.c:(.text+0x5d1c): undefined reference to `kempld_read8'
kempld_wdt.c:(.text+0x5d2c): undefined reference to `kempld_write8'