MVEBUMMC : Speed up access time

Get about 40x faster access on SHEEVAPLUG MMC
 Fix some SD type compatibility

 Changes in v3:
 - fix the HW_STATE (from linux mvsdio)
 - review delays and timeouts

 Changes in v2:
 - increase number of loops
 - remove initial delay

 Changes in v1:
 - review all loops, delays and timeouts

Signed-off-by: Gérald Kerma <drEagle@doukki.net>
Acked-by: Pantelis Antoniou <panto@antoniou-consulting.com>