[media] mantis: add remote control support

The embedded UART is apparently used to receive decoded IR (RC5?) codes.
Forward these scan codes to the RC framework and (where known) add
corresponding mapping tables to translate them into regular keys.

This patch has been tested on a TechniSat CableStar HD2. The mappings of other
rc-maps were taken from Christoph Pinkl's patch
(http://patchwork.linuxtv.org/patch/7217/

) and the s2-liplianin repository. The
major difference to Christoph's patch is a reworked interrupt handling of the
UART because the RX interrupt is apparently level triggered and requires
masking until the FIFO is read by the UART worker.

Signed-off-by: Jan Klötzke <jan@kloetzke.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>