media: i2c: alvium: Move V4L2_CID_GAIN to V4L2_CID_ANALOG_GAIN

Into alvium cameras REG_BCRM_GAIN_RW control the analog gain.
Let's use the right V4L2_CID_ANALOGUE_GAIN ctrl.

Fixes: 0a7af872 ("media: i2c: Add support for alvium camera")
Cc: stable@vger.kernel.org
Signed-off-by: Tommaso Merciai <tomm.merciai@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>