ARM: sunxi: dts: split IR pins for A10 and A20

Currently none of the target boards nor the driver supports
IR TX. However this pin is used in a few instances as a GPIO.
Split the pin ctrl descriptions so that only the IR RX is
configured to be used.

Signed-off-by: Marcus Cooper <codekipper@gmail.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>