jfs: UBSAN: shift-out-of-bounds in dbFindBits

Fix issue with UBSAN throwing shift-out-of-bounds warning.

Reported-by: [email protected]
Signed-off-by: Remington Brasga <[email protected]>
Signed-off-by: Dave Kleikamp <[email protected]>

Author: rbrasga

fs/jfs/jfs_dmap.c

@@ -3022,7 +3022,7 @@ static int dbFindBits(u32 word, int l2nb)
 
 	/* scan the word for nb free bits at nb alignments.
 	 */
-	for (bitno = 0; mask != 0; bitno += nb, mask >>= nb) {
+	for (bitno = 0; mask != 0; bitno += nb, mask = (mask >> nb)) {
 		if ((mask & word) == mask)
 			break;
 	}