media: i2c: imx290: Fix max gain value

The gain is expressed in multiple of 0.3dB, as a value between 0.0dB
and 72.0dB. Gains between 0.0dB and 30.0dB (included) apply analog gain
only, higher gains from 30.3dB to 72dB apply additional digital gain.

The maximum gain value is erroneously set to 72. Increase it to 100 to
cover the whole analog gain range. Support for digital gain can be added
separately if needed.

The IMX327 and IMX462 are largely compatible with the IMX290, but have
an analog gain range of 0.0dB to 29.4dB and 42dB of digital gain. When
support for those sensors gets added to the driver, the gain control
should be adjusted accordingly.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>