media: imx7-media-csi: Use devm_platform_ioremap_resource()

Use devm_platform_ioremap_resource() to simplify the code a bit.

While at it, propagate the real error value in case of
devm_platform_ioremap_resource() failure.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Tested-by: Rui Miguel Silva <rmfrfs@gmail.com>
Reviewed-by: Rui Miguel Silva <rmfrfs@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>