AT91 MMC 1: Pass host structure.

The I/O base address is now stored in the 'at91mci_host' structure.  We
therefore have to pass this structure to at91_mci_read() and
at91_mci_write().
Signed-off-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>