[WATCHDOG] improve machzwd detection

On a machine with no machzwd, loading the module prints out..

machzwd: MachZ ZF-Logic Watchdog driver initializing.
0xffff
machzwd: Watchdog using action = RESET

- the 0xffff printk is unnecessary
- 0xffff seems to be 'hardware not present'
- fix CodingStyle. (This driver could use some more work here)

Signed-off-by: Dave Jones <davej@redhat.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Andrew Morton <akpm@osdl.org>