mmc: queue: issue requests when dcmd is in progress

Requests can still be issued when dcmd is in progress.
Only when discard is in progress, should the requests not
be issued.

Change-Id: Ief70cf2f86e9eb3817f8a390626be8433180ed87
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Venkat Gopalakrishnan <venkatg@codeaurora.org>