[En-Nut-Discussion] support for SD-HC cards

[PragmaLab]

Hello all,

I just finished making the modifications in the code to support SD-HC (high
capacity) cards. The changes needed to support HC-cards are best described
by:

1) new way of initialising the card (new command 'MMCMD_SEND_IF_COND' is
introduced in a new init-sequence)
2) layout of CSD register has changed (no impact, since the code does not
use it)
3) HC-cards use block addressing iso byte-addressing
4) HC-cards use fixed timeouts (no impact, not used in the code)

Regarding 2) I noticed that the code uses the info it finds in the partion
table to get the total number of sectors and does not read the CSD register
for that. This way the new layout for CSD in HC-cards has no implications
for the code.

Most modifications are made in mmcard.c and mmcard.h. If somebody wants to
add it to the CVS-head, just let me know. I tested it with 4 GB SD-HC cards.

Best regards,

Rob van Lieshout

ps: Harald, I did not come across any pattent issues when it comes to using
SD-HC cards. We just use it in SPI-mode....