media: i2c: ov9282: Correct the exposure offset

[ Upstream commit feaf4154 ]

The datasheet lists that "Maximum exposure time is frame
length -25 row periods, where frame length is set by
registers {0x380E, 0x380F}".
However this driver had OV9282_EXPOSURE_OFFSET set to 12
which allowed that restriction to be violated, and would
result in very under-exposed images.

Correct the offset.

Fixes: 14ea315b ("media: i2c: Add ov9282 camera sensor driver")
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>