media: i2c: imx258: add HDR control

The IMX258 supports High Dynamic Range with 5 levels of low/high
exposure ratio.  Add a V4L2 control for HDR (WIDE_DYNAMIC_RANGE).

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>