This patch adds MMC over SPI support to mci-core.c and
mci_spi.c driver.
This driver is useful when SOC doesn't have built-in MCI
component. Tested with nios, 2Go SD-CARD and FAT file system.
Signed-off-by: Franck Jullien <franck.jullien@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>