mmc: core: Call cmdq_post_req with tag info instead of mrq

Call mmc_/cmdq_post_req with tag number instead of
mrq. This is needed in error handling as part of multiple
request error handling.

Change-Id: I175432639d28378ec74669e31deb4d1667c49bb8
Signed-off-by: Ritesh Harjani <riteshh@codeaurora.org>