arm: kirkwood: remove non-dm MMC driver init

No board uses this driver any more: remove it.

Signed-off-by: Harm Berntsen <harm.berntsen@nedap.com>
Reviewed-by: Stefan Roese <sr@denx.de>
CC: Gerald Kerma <drEagle@doukki.net>
CC: Stefan Roese <sr@denx.de>
CC: Pantelis Antoniou <panto@antoniou-consulting.com>