sunxi-mmc: use new mode on both controllers on A64

Using new mode improves stability of eMMC and SD cards. Without
it SPL fails to load u-boot from SD on Pinebook.

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Tested-by: Jagan Teki <jagan@amarulasolutions.com> # Amarula A64-Relic
Reviewed-by: Jagan Teki <jagan@openedev.com>