ARM: dts: sun7i: Add uart3/4/5, i2c3 and spi2 pinmux

This patch add generic dts node for uart3/4/5, i2c3 and spi2.

Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Wills Wang <wills.wang.open@gmail.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>