hfs: ensure sb->s_fs_info is always cleaned up

In the Linux kernel, the following vulnerability has been resolved:

hfs: ensure sb->s_fs_info is always cleaned up

When hfs was converted to the new mount api a bug was introduced by changing the allocation pattern of sb->s_fs_info. If setup_bdev_super() fails after a new superblock has been allocated by sget_fc(), but before hfs_fill_super() takes ownership of the filesystem-specific s_fs_info data it was leaked.

Fix this by freeing sb->s_fs_info in hfs_kill_super().