media: i2c: imx296: Add horizontal/vertical flip support

Add support for setting horizontal and/or vertial flips in the IMX296
sensor through the V4L2_CID_HFLIP and V4L2_CID_VFLIP controls.

Add a new helper function to return the media bus format code that
depends on the sensor flips.

Grab the V4L2_CID_HFLIP and V4L2_CID_VFLIP controls on stream on, and
release on stream off to ensure flips cannot be changed while the sensor
is streaming.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>