ARM: dts: sun9i: Use sun9i specific mmc compatible

sun9i/A80 MMC controllers have a larger FIFO, and the FIFO DMA
trigger levels can be increased. Also, the mmc module clock parent
has a higher clock rate, and the sample and output delay phases
are different.

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