[media] tvp514x: s_routing should just change routing, not try to detect a signal

The s_routing function should not try to detect a signal. It is a really
bad idea to try to detect a valid video signal and return an error if
you can't. Changing input should do just that and nothing more.
Also don't power on the ADCs on s_routing, instead do that on querystd.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Lad, Prabhakar <prabhakar.lad@ti.com>
Tested-by: Lad, Prabhakar <prabhakar.lad@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>