[media] rc-core: don't treat dev->rc_map.rc_type as a bitmap

store_protocols() treats dev->rc_map.rc_type as a bitmap which is wrong for
two reasons. First of all, it is pretty bogus to change the protocol type of
the keymap just because the hardware has been asked to decode a different
protocol.
Second, dev->rc_map.rc_type is an enum (i.e. a single protocol) as pointed
out by James Hogan <james.hogan@imgtec.com>.
Fix both issues by introducing a separate enabled_protocols member to
struct rc_dev.

Signed-off-by: David Härdeman <david@hardeman.nu>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>