drm/imx/dcss: request memory region

The driver's memory regions are currently just ioremap()ed, but not
reserved through a request. That's not a bug, but having the request is
a little more robust.

Implement the region-request through the corresponding managed
devres-function.

Signed-off-by: Philipp Stanner <pstanner@redhat.com>
Reviewed-by: Laurentiu Palcu <laurentiu.palcu@oss.nxp.com>
Signed-off-by: Laurentiu Palcu <laurentiu.palcu@oss.nxp.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240124111904.18261-3-pstanner@redhat.com