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>