mmc: Add support for the Marvell Dove SDHCI controller

Implement an sdhci-pltfm driver for the controller found in the
Marvell Dove SoC.

Signed-off-by: Mike Rapoport <mike@compulab.co.il>
CC: Saeed Bishara <saeed@marvell.com>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Chris Ball <cjb@laptop.org>