btrfs: cleanup, use kmalloc_array/kcalloc array helpers

Convert kmalloc(nr * size, ..) to kmalloc_array that does additional
overflow checks, the zeroing variant is kcalloc.

Signed-off-by: David Sterba <dsterba@suse.cz>
diff --git a/fs/btrfs/check-integrity.c b/fs/btrfs/check-integrity.c
index d897ef8..089d6fa 100644
--- a/fs/btrfs/check-integrity.c
+++ b/fs/btrfs/check-integrity.c
@@ -2990,8 +2990,8 @@
 			       (unsigned long long)bio->bi_iter.bi_sector,
 			       dev_bytenr, bio->bi_bdev);
 
-		mapped_datav = kmalloc(sizeof(*mapped_datav) * bio->bi_vcnt,
-				       GFP_NOFS);
+		mapped_datav = kmalloc_array(bio->bi_vcnt,
+					     sizeof(*mapped_datav), GFP_NOFS);
 		if (!mapped_datav)
 			goto leave;
 		cur_bytenr = dev_bytenr;