sata_rcar: Convert to devm_ioremap_resource()

Use the newly introduced devm_ioremap_resource() instead of
devm_request_and_ioremap() which provides more consistent error handling.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Acked-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>