ARM: dts: sun6i: Add pin-muxing info for the mmc controllers

This adds  pin-muxing info for the mmc controller / port combinations which
are known to be used on actual boards.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>