[WATCHDOG] fix watchdog/wdt285.c compilation

This patch fixes the following compile error caused by
commit d0e58eed


([WATCHDOG 55/57] wdt285: switch to unlocked_ioctl and tidy up ...):

<--  snip  -->

...
  CC [M]  drivers/watchdog/wdt285.o
wdt285.c: In function 'footbridge_watchdog_init':
wdt285.c:211: error: 'KERN_WARN' undeclared (first use in this function)
wdt285.c:211: error: (Each undeclared identifier is reported only once
wdt285.c:211: error: for each function it appears in.)
wdt285.c:212: error: expected ')' before string constant
make[3]: *** [drivers/watchdog/wdt285.o] Error 1

<--  snip  -->

Reported-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>