[media] rc-core: rename ir-raw.c

Better to be coherent and prefix this file with rc-, in order to
help to identify to what subsystem it belongs.

This is in preparaton for a latter patch that will transform the
raw handling into a separate module.

Signed-off-by: David Härdeman <david@hardeman.nu>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>