watchdog: hpwdt (1/12): clean-up include-files.

* remove unnecessary includes
* We use a spinlock, but lacked the include
* We need bitops.h for test_and_set_bit/clear_bit

Signed-off-by: dann frazier <dannf@hp.com>
Acked-by: Thomas Mingarelli <Thomas.Mingarelli@hp.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>