ceph: mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
[idryomov@gmail.com: amended "Older OSDs" comment]
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
diff --git a/net/ceph/ceph_hash.c b/net/ceph/ceph_hash.c
index 67bb1f1..9a5850f2 100644
--- a/net/ceph/ceph_hash.c
+++ b/net/ceph/ceph_hash.c
@@ -47,28 +47,38 @@ unsigned int ceph_str_hash_rjenkins(const char *str, unsigned int length)
 
 	/* handle the last 11 bytes */
 	c = c + length;
-	switch (len) {            /* all the case statements fall through */
+	switch (len) {
 	case 11:
 		c = c + ((__u32)k[10] << 24);
+		/* fall through */
 	case 10:
 		c = c + ((__u32)k[9] << 16);
+		/* fall through */
 	case 9:
 		c = c + ((__u32)k[8] << 8);
 		/* the first byte of c is reserved for the length */
+		/* fall through */
 	case 8:
 		b = b + ((__u32)k[7] << 24);
+		/* fall through */
 	case 7:
 		b = b + ((__u32)k[6] << 16);
+		/* fall through */
 	case 6:
 		b = b + ((__u32)k[5] << 8);
+		/* fall through */
 	case 5:
 		b = b + k[4];
+		/* fall through */
 	case 4:
 		a = a + ((__u32)k[3] << 24);
+		/* fall through */
 	case 3:
 		a = a + ((__u32)k[2] << 16);
+		/* fall through */
 	case 2:
 		a = a + ((__u32)k[1] << 8);
+		/* fall through */
 	case 1:
 		a = a + k[0];
 		/* case 0: nothing left to add */