mmc: core: remove bkops_busy flag from the mmc_command structure

As "bkops_busy" flag is no longer used, remove it from the mmc_command
structure.

Change-Id: I739030e90d37ce40a484a072e604a0e398b2872e
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>