[media] rc/mce: add mappings for missing keys

Per http://mediacenterguides.com/book/export/html/31

 and investigation
by Erin, we were missing these last three mappings to complete the mce
key table. Lets remedy that.

Reported-by: Erin Simonds <fisslefink@gmail.com>
Signed-off-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>