media: mxb: update the tvnorms when changing input

The tuner input uses different tvnorms compared to the
S-Video/Composite inputs. So update the tvnorms field
in struct video_device when switching inputs.

This fixes a V4L2 compliance issue.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>