configs: openrd: remove non-dm MMC driver

Unfortunately this board has no DM support at all. We are also way past
the deadline for driver model support for various devices on this board.

Signed-off-by: Harm Berntsen <harm.berntsen@nedap.com>
Reviewed-by: Stefan Roese <sr@denx.de>
CC: Stefan Roese <sr@denx.de>