Enabled NFS root related options
Allow to specify which fields in mmc_ios have changed
A huge amount of improvemets...

After this, the code is able to send a couple of commands
and even get the reply from the card.

Tested on a "normal" SD memory-only SDHC card.
Implement sending application command 41

This allows to get an OCR of the card.
A simple solution to retry sending APPCMD+ACMD41 is implemented
by setting the proper state for the FSM. This needs to be tuned
so it doesn't go to the infinite loop if the card doesn't answer at all.