media: i2c: imx258: Implement HFLIP and VFLIP controls.

The sensor supports H & V flips, so implement the relevant controls.
Note that the Bayer order changes with these flips, therefore
they set the V4L2_CTRL_FLAG_MODIFY_LAYOUT property.

As we now support flips, remove the restriction of the sensor only
probing if rotated 180 degrees, but do take that value and initialise
VFLIP and HFLIP based on it.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>