mmc: sunxi: support cd-inverted

mmc: sunxi: support cd-inverted

With CONFIG_DM_MMC the BananaPi does not detect SD cards.

The sunxi device trees use the cd-inverted property to indicate that
the card detect is inverted.

This property is documented in Linux kernel devicetree/bindings/mmc/mmc.txt
The property is not marked as deprecated.

A similar patch was posted by Tuomas but is in status "Changes Requested".
https://patchwork.ozlabs.org/patch/850377/

This patch is a stripped down version of his patch.

Suggested-by: Tuomas Tynkkynen <tuomas@tuxera.com>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>