omap: Update MMC response types

This patch is a fix in order to update MMC response types. This modification is
needed to allow SD card support on OMAP platforms.

Signed-off-by: Carlos Eduardo Aguiar <carlos.aguiar@indt.org.br>
Signed-off-by: Yuha Yrjola <juha.yrjola@solidboot.com>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>