media: rc: meson-ir: rename Meson IR Controller register macros

There are more registers to come in the next Meson IR Controller.
For defining clearly, rename register macros.

Signed-off-by: Zelong Dong <zelong.dong@amlogic.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>