mmc: card: Fix use of uninitialized data in mmc_blk_issue_rw_rq.

mmc_blk_issue_rw_rq did not zero out mmc_command on stack.
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/card/block.c

@@ -504,6 +504,7 @@ static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *req)
 		struct mmc_command cmd;
 		u32 readcmd, writecmd, status = 0;
 
+		memset(&cmd, 0, sizeof(struct mmc_command));
 		memset(&brq, 0, sizeof(struct mmc_blk_request));
 		brq.mrq.cmd = &brq.cmd;
 		brq.mrq.data = &brq.data;