booke/wdt: some ioctls do not return values properly

Fix some booke wdt ioctls return value error.

Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
Acked-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>