MMC_CAP_SD_HIGHSPEED is not supported on Snowball board resulting on
initialization errors.

Cc: stable@kernel.org
Signed-off-by: NMathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: NFredrik Soderstedt <fredrik.soderstedt@stericsson.com>
Signed-off-by: NPhilippe Langlais <philippe.langlais@linaro.org>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>