ARM: sunxi-mmc: Add mmc support for sun6i / A31

ARM: sunxi-mmc: Add mmc support for sun6i / A31

The mmc hardware on sun6i has an extra reset control that needs to
be de-asserted prior to usage. Also the FIFO address is different.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
[wens@csie.org: use setbits_le32 for reset control, drop obsolete changes,
		rewrite different FIFO address handling, add commit message]
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Ian Campbell <ijc@hellion.org.uk>