mtdoops: fix the oops_page_used array size

The array of unsigned long pointed by oops_page_used is allocated
by vmalloc which requires the size to be in bytes.

BITS_PER_LONG is equal to 32.
If we want to allocate memory for 32 pages with one bit per page then
32 / BITS_PER_LONG  is equal to 1 byte that is 8 bits.
To fix it we need to multiply the result by sizeof(unsigned long) equal to 4.

Cc: stable@kernel.org
Signed-off-by: Roman Tereshonkov <roman.tereshonkov@nokia.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/mtdoops.c

@@ -372,7 +372,7 @@ static void mtdoops_notify_add(struct mtd_info *mtd)
 
 	/* oops_page_used is a bit field */
 	cxt->oops_page_used = vmalloc(DIV_ROUND_UP(mtdoops_pages,
-			BITS_PER_LONG));
+			BITS_PER_LONG) * sizeof(unsigned long));
 	if (!cxt->oops_page_used) {
 		printk(KERN_ERR "mtdoops: could not allocate page array\n");
 		return;