media: synopsys: csi2rx: use devm_reset_control_get_optional_exclusive()

media: synopsys: csi2rx: use devm_reset_control_get_optional_exclusive()

The DW MIPI CSI-2 RX is used on different SoCs, not all of which provide a
reset controller. Switch to devm_reset_control_get_optional_exclusive()
to support such platforms.

Reset presence and numbering are validated by the DT binding.

Reviewed-by: Michael Riesch <michael.riesch@collabora.com>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>