drivers/mtd: Use kmemdup

Use kmemdup when some other buffer is immediately copied into the
allocated region.

A simplified version of the semantic patch that makes this change is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@@
expression from,to,size,flag;
statement S;
@@

-  to = \(kmalloc\|kzalloc\)(size,flag);
+  to = kmemdup(from,size,flag);
   if (to==NULL || ...) S
-  memcpy(to, from, size);
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/mtdconcat.c

@@ -183,10 +183,9 @@ concat_writev(struct mtd_info *mtd, const struct kvec *vecs,
 	}
 
 	/* make a copy of vecs */
-	vecs_copy = kmalloc(sizeof(struct kvec) * count, GFP_KERNEL);
+	vecs_copy = kmemdup(vecs, sizeof(struct kvec) * count, GFP_KERNEL);
 	if (!vecs_copy)
 		return -ENOMEM;
-	memcpy(vecs_copy, vecs, sizeof(struct kvec) * count);
 
 	entry_low = 0;
 	for (i = 0; i < concat->num_subdev; i++) {