MMC/SD card driver learns SPI

Teaching the MMC/SD block card driver about SPI.

 - Provide the SPI response type flags with each request issued.

 - Understand that multiblock SPI writes don't use STOP_TRANSMISSION.

 - Correct check for APP_CMD failure.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>