watchdog: ie6xx_wdt.c: fix printk format warning

Fix printk format warning; use cast to u64 since resource_size_t can
be either u32 or u64.

drivers/watchdog/ie6xx_wdt.c:261:4: warning: format '%x' expects type 'unsigned int', but argument 3 has type 'resource_size_t'

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>