media: i2c: ov9282: Add selection for CSI2 clock mode

The sensor supports either having the CSI2 clock lane free
running, or gated when there is no packet to transmit.
The driver only selected gated (non-continuous) clock mode.

Add code to allow fwnode to configure whether the clock is
gated or free running.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>