mmc: mv_sdhci: add driver model support

The new DM implementation currently does not support the Sheeva
88SV331xV5 specific quirk present in the legacy implementation. The
legacy code is thus kept for this SoC and others not yet migrated to
DM_MMC.

Signed-off-by: Pierre Bourdon <delroth@gmail.com>
Cc: Jaehoon Chung <jh80.chung@samsung.com>
Cc: Stefan Roese <sr@denx.de>
Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Stefan Roese <sr@denx.de>