incorrect CONFIG_SYS_MMC_ENV_DEV define

"MMC Device 3 not found" if CONFIG_MMC_SUNXI_SLOT = 3

Signed-off-by: Wills Wang <wills.wang.open@gmail.com>
Signed-off-by: Henrik Nordstrom <henrik@henriknordstrom.net>
support for MMC card

MMC driver check TIMEOUT to determine if it is MMC card.

Signed-off-by: Wills Wang <wills.wang.open@gmail.com>
Signed-off-by: Henrik Nordstrom <henrik@henriknordstrom.net>
support for extra/secondary SD/MMC card

Signed-off-by: Wills Wang <wills.wang.open@gmail.com>
Signed-off-by: Henrik Nordstrom <henrik@henriknordstrom.net>