[media] solo6x10: move global fields in solo_enc_fh to solo_enc_dev

All fields in solo_enc_fh do not belong there since they refer to global
properties. After moving all these fields to solo_enc_dev the solo_dev_fh
struct can be removed completely.
Note that this also kills the 'listener' feature of this driver. This
feature (where multiple filehandles can read the video) is illegal in the
V4L2 API. Do this in userspace: it's much more efficient to copy memory
than it is to DMA to every listener.

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