msm: watchdog-v2: use request_mem_region instead of request_region

Use request_mem_region api to request for allocating io resource in place
of request_region since the resource is actually not an io port resource
but io memory.

Change-Id: Iddb279466495e34aa469dabaa134a209db2e21ea
Signed-off-by: Aparna Das <adas@codeaurora.org>