[media] rc: rc-core: Add support for encode_wakeup drivers

Add support in rc-core for drivers which implement the wakeup scancode
filter by encoding the scancode using the raw IR encoders. This is by
way of rc_dev::encode_wakeup which should be set to true to make the
allowed wakeup protocols the same as the set of raw IR encoders.

As well as updating the sysfs interface to know which wakeup protocols
are allowed for encode_wakeup drivers, also ensure that the IR
decoders/encoders are loaded when an encode_wakeup driver is registered.

Signed-off-by: James Hogan <james@albanarts.com>
Signed-off-by: Antti Seppälä <a.seppala@gmail.com>
Cc: David Härdeman <david@hardeman.nu>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>