UBI: use GFP_NOFS properly

This patch fixes a brown-paperbag bug which was introduced by me:
I used incorrect "GFP_KERNEL | GFP_NOFS" allocation flags to make
sure my allocations do not cause write-back. But the correct form
is "GFP_NOFS".
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

drivers/mtd/ubi/io.c

@@ -1345,7 +1345,7 @@ int ubi_dbg_check_write(struct ubi_device *ubi, const void *buf, int pnum,
 	if (!(ubi_chk_flags & UBI_CHK_IO))
 		return 0;
 
-	buf1 = __vmalloc(len, GFP_KERNEL | GFP_NOFS, PAGE_KERNEL);
+	buf1 = __vmalloc(len, GFP_NOFS, PAGE_KERNEL);
 	if (!buf1) {
 		ubi_err("cannot allocate memory to check writes");
 		return 0;
@@ -1409,7 +1409,7 @@ int ubi_dbg_check_all_ff(struct ubi_device *ubi, int pnum, int offset, int len)
 	if (!(ubi_chk_flags & UBI_CHK_IO))
 		return 0;
 
-	buf = __vmalloc(len, GFP_KERNEL | GFP_NOFS, PAGE_KERNEL);
+	buf = __vmalloc(len, GFP_NOFS, PAGE_KERNEL);
 	if (!buf) {
 		ubi_err("cannot allocate memory to check for 0xFFs");
 		return 0;