[media] v4l2-ioctl.c: move a block of code down, no other changes

A block of code is moved down in the code to make later changes easier.
Do just the move without other changes to keep the diff readable for the
upcoming patch.

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