mmc: core: mmc_blk_rw_cmd_err - remove unused variable

Fix compilation warning:

drivers/mmc/core/block.c:1563:24: warning: variable ‘mq_rq’ set but not
used [-Wunused-but-set-variable]  struct mmc_queue_req *mq_rq;
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/block.c

@@ -1560,11 +1560,8 @@ static bool mmc_blk_rw_cmd_err(struct mmc_blk_data *md, struct mmc_card *card,
 			       struct mmc_blk_request *brq, struct request *req,
 			       bool old_req_pending)
 {
-	struct mmc_queue_req *mq_rq;
 	bool req_pending;
 
-	mq_rq = container_of(brq, struct mmc_queue_req, brq);
-
 	/*
 	 * If this is an SD card and we're writing, we can first
 	 * mark the known good sectors as ok.