[WATCHDOG] watchdog miscdevice patch

It looks like the recent changes to 'struct miscdevice' have impacted
some of the Watchdog drivers.

at91rm9200_wdt.c:205: error: 'struct miscdevice' has no member named 'dev'

For the AT91RM9200 driver I just replaced "miscdevice.dev" with
"miscdevice.parent".

The mpcore_wdt.c and omap_wdt.c seem similarly affected.

Signed-off-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>