[media] solo6x10: reimplement SAA712x setup routine

This cleans up the saa712x setup code and there are no functional changes.

Signed-off-by: Ismael Luceno <ismael.luceno@corp.bluecherry.net>
[hans.verkuil@cisco.com: add clarification that this is cleanup only]
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>