[media] hexium-gemini: remove B&W control, fix input table

The B&W control never worked, and you get the same effect by setting saturation to the
lowest value. So it has been removed. Also fixed some incorrect entries in the input
table. This driver now passes v4l2-compliance.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>