sunxi: mmc: Always declare High Capacity capability

High Capacity (e)MMC cards work fine on sun4i / sun5i, and not having this
capability set causes u-boot to not recognize the eMMC on an Utoo P66 A13
tablet, so always set it thereby fixing this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>