watchdog: Fix warning

This seems to have popped up after the recent merges:

drivers/watchdog/w83697ug_wdt.c: In function ‘w83697ug_select_wd_register’:
drivers/watchdog/w83697ug_wdt.c:105: warning: ‘return’ with a value, in function returning void

Signed-off-by: Alan Cox <alan@redhat.com>
Acked-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>