[media] rc: Properly name the rc_map struct

The struct that describes a rc mapping had an weird and long name.
We should properly name it, to make easier for developers to work
with it, and to avoid confusion.

Basically, generated by this script:

for i in `find drivers/staging -type f -name *.[ch]` `find include/media -type f -name *.[ch]` `find drivers/media -type f -name *.[ch]`; do sed s,ir_scancode_table,rc_map,g <$i >a && mv a $i; done
for i in `find drivers/staging -type f -name *.[ch]` `find include/media -type f -name *.[ch]` `find drivers/media -type f -name *.[ch]`; do sed s,rc_tab,rc_map,g <$i >a && mv a $i; done

(and manually fixed where needed)

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>