media: rc: sunxi: Add A31 compatible

Allwiner A31 has a different memory mapping so add the compatible
we will need it later.

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>