media: ar0521: Adjust exposure and blankings limits

Adjust the control limits for V4L2_CID_VBLANK, V4L2_CID_HBLANK and
V4L2_CID_EXPOSURE when a new format is applied to the sensor.

Update the exposure control limits when a new blanking value is
applied and change the controls initialization to use valid values for the
default format.

The exposure control default value is changed to report the default
value of register 0x3012.

Signed-off-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>