mmc: core: Use kmalloc_array() in mmc_alloc_sg()

* A multiplication for the size determination of a memory allocation
  indicated that an array data structure should be processed.
  Thus use the corresponding function "kmalloc_array".

  This issue was detected by using the Coccinelle software.

* Replace the specification of a data structure by a pointer dereference
  to make the corresponding size determination a bit safer according to
  the Linux coding style convention.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/queue.c

@@ -152,7 +152,7 @@ static struct scatterlist *mmc_alloc_sg(int sg_len, int *err)
 {
 	struct scatterlist *sg;
 
-	sg = kmalloc(sizeof(struct scatterlist)*sg_len, GFP_KERNEL);
+	sg = kmalloc_array(sg_len, sizeof(*sg), GFP_KERNEL);
 	if (!sg)
 		*err = -ENOMEM;
 	else {