media: dt-bindings: media: sun6i: Add A64 CSI compatible

Allwinner A64 CSI is a single channel time-multiplexed BT.656
protocol interface.

Add separate compatible string for A64 since it require explicit
change in sun6i_csi driver to update default CSI_SCLK rate.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>