hpwdt: don't use static flags

Static (read: global) is potential problem.  Two threads can corrupt each
other's interrupt status, better avoid this.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Wim Van Sebroeck <wim@iguana.be>
Cc: Thomas Mingarelli <thomas.mingarelli@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>