watchdog: Use DEFINE_SPINLOCK() for static spinlocks

Rather than just defining static spinlock_t variables and then
initializing them later in init functions, simply define them with
DEFINE_SPINLOCK() and remove the calls to spin_lock_init().

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Cc: Nicolas Thill <nico@openwrt.org>
Cc: Heiko Ronsdorf <hero@ihg.uni-duisburg.de>
Cc: Rodolfo Giometti <giometti@ascensit.com>
Cc: Andrey Panin <pazke@donpac.ru>
Cc: Guido Guenther <agx@sigxcpu.org>
Cc: Curt E Bruns <curt.e.bruns@intel.com>
Cc: Deepak Saxena <dsaxena@plexity.net>
Cc: Andrew Victor <linux@maxim.org.za>
Cc: George G. Davis <gdavis@mvista.com>
Cc: Sylver Bruneau <sylver.bruneau@googlemail.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>