[media] omap3isp: Use devm_ioremap_resource()

Replace devm_request_mem_region() and devm_ioremap_nocache() with
devm_ioremap_resource(). The behaviour remains the same and the code is
simplified.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>