watchdog: twl4030_wdt: Disable watchdog during probing

If we are not able to register then it is better to have
watchdog in disabled state than noticing a system reboot.

Signed-off-by: Ameya Palande <ameya.palande@nokia.com>
Acked-By: Timo Kokkonen <timo.t.kokkonen@nokia.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>