mmc: core: do not reinsert prepeared FUA and FLUSH requests in stop flow

When mmc context has unblocked from waiting current request because of
urgent request notification coming from block layer, there is prepeared
request.  In the case, when the request is REQ_FUA or REQ_FLUSH, the
flow should not reinsert it back to i/o scheduler (since according to
block layer logic flush requests with data should never enter elevator).
Instead this request starts immediately.

Change-Id: Ia78b56c6135dd1a8d75a98fd5b771a5035e5c360
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>