mmc: fixes for eMMC v4.5 sanitize operation

eMMC v4.5 sanitize operation erases all copies of unmapped
data.  However trim or erase operations must be used first
to unmap the required sectors.  That was not being done.

Fixes apply to linux 3.2 on.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: <stable@vger.kernel.org>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>