mmc: Remove unused variable backup from mmc_send_cmd()

Do not call a memset for unused variable backup every time.
Remove unused variable from function.

Signed-off-by: Oleksandr Tyshchenko <oleksandr.tyshchenko@ti.com>
Acked-by: Pantelis Antoniou <panto@antoniou-consulting.com>
diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index 5502675..0b552f5 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -55,11 +55,8 @@
 static int mmc_send_cmd(struct mmc *mmc, struct mmc_cmd *cmd,
 			struct mmc_data *data)
 {
-	struct mmc_data backup;
 	int ret;
 
-	memset(&backup, 0, sizeof(backup));
-
 #ifdef CONFIG_MMC_TRACE
 	int i;
 	u8 *ptr;