ARM: dts: Add mshc aliases for rk3288

It's convenient (and less confusing to people reading logs) if the
eMMC port on rk3288 is consistenly marked with mmc0 and the sdmmc port
on rk3288 is consistently marked with mmc1.  Add the appropriate
aliases.

Signed-off-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Sonny Rao <sonnyrao@chromium.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>