media: i2c: alvium: enable acquisition frame rate

Alvium camera by default is in free running mode. Datasheet say that
acquisition frame rate reg can only be used if frame start trigger
mode is set to off.
Enable r/w acquisition frame rate and turn off trigger mode.

Signed-off-by: Tommaso Merciai <tomm.merciai@gmail.com>
[Sakari Ailus: Fix spelling of "acquisition".]
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>