Most cards do not answer if some reserved bits
in the ocr are set. However, some controllers
can set bit 7 (reserved for low voltages), but
how to manage low voltages SD card is not yet
specified.
based on the original U-Boot patch from
Stefano Babic <sbabic@denx.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>