ext2: Fix fall-through warnings for Clang

In preparation to enable -Wimplicit-fallthrough for Clang, fix a warning
by explicitly adding a break statement instead of just letting the code
fall through to the next case.

Link: KSPP/linux#115
Link: https://lore.kernel.org/r/73d8ae2d06d639815672ee9ee4550ea4bfa08489.1605896059.git.gustavoars@kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/ext2/inode.c

@@ -1256,6 +1256,7 @@ static void __ext2_truncate_blocks(struct inode *inode, loff_t offset)
 				mark_inode_dirty(inode);
 				ext2_free_branches(inode, &nr, &nr+1, 3);
 			}
+			break;
 		case EXT2_TIND_BLOCK:
 			;
 	}