mmc: queue: do not clean current request when urgent in progress

As a result of following fix: "mmc: core: do not reinsert prepeared
FUA and FLUSH requests in stop flow" REQ_FUA and REQ_FLUSH requests
are not reinserted back into i/o scheduler, but instead started request
execution.

This change will prevent cleaning current request pointer for such
requests.

Change-Id: I25f8706954fb538be62182c87d5fb20354696b7a
CRs-fixed: 600127
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>