mmc: Resolve BKOPS compatability issue

This patch is coming to fix compatibility issue of BKOPS_EN  field of EXT_CSD.
In eMMC-5.1, BKOPS_EN was changed, and now it has two operational bits:
Bit 0 - MANUAL_EN
Bit 1 - AUTO_EN
In previous eMMC revisions, only Bit 0 was supported.

Signed-off-by: Alexey Skidanov <alexey.skidanov@sandisk.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>