media: rc: update sunxi-ir driver to get base clock frequency from devicetree

This patch updates the sunxi-ir driver to set the base clock frequency from
devicetree.

This is necessary since there are different ir receivers on the
market, that operate with different frequencies. So this value could be
set if the attached ir receiver needs a different base clock frequency,
than the default 8 MHz.

Signed-off-by: Philipp Rossak <embed3d@gmail.com>
Reviewed-by: Andi Shyti <andi.shyti@samsung.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>