media: rc: sunxi: Add RXSTA bits definition

We are using RXINT bits definition when looking at RXSTA register.

These bits are equal but it's not really proper.

Introduce the RXSTA bits and use them to have coherency.

Signed-off-by: Clément Péron <peron.clem@gmail.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>