[media] vivid: BT.2020 R'G'B' is limited range

According to the standard the R'G'B' BT.2020 colorspace is limited
range, not full range. Fix this.

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