media: imx258: Check the rotation property has a value of 180

The driver only supports streaming images flipped horizontally and
vertically. In order to ensure that all current users will be fine if or
when support for upright streaming is added, require the presence of the
"rotation" control now.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Tested-by: "Lai, Jim" <jim.lai@intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>