media: v4l2-mediabus: Drop V4L2_MBUS_CSI2_CONTINUOUS_CLOCK flag

MIPI CSI-2 continuous and non-continuous clock modes are mutually
exclusive. Drop the V4L2_MBUS_CSI2_CONTINUOUS_CLOCK flag and use
V4L2_MBUS_CSI2_NONCONTINUOUS_CLOCK only.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>