ARM: dts: sun4i: Provide default muxing for relevant controllers

The I2C's, MMC0 and EMAC controllers have only one muxing option in the
SoC. In such a case, we can just move the muxing into the DTSI, and remove
it from the DTS.

Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>