media: i2c: adv7180: fix reserved bit in Video Selection 2

This bit is marked as reserved in the ADV Hardware Reference Manual.

Resetting this bit seems to cause increased video noise. Setting this
bit according to the Hardware Reference Manual reduces the video noise
immediately.

Signed-off-by: Benjamin Marty <info@benjaminmarty.ch>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Tested-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>