virtiofs: drop __exit from virtio_fs_sysfs_exit()

virtiofs: drop __exit from virtio_fs_sysfs_exit()

virtio_fs_sysfs_exit() is called by:
- static int __init virtio_fs_init(void)
- static void __exit virtio_fs_exit(void)

Remove __exit from virtio_fs_sysfs_exit() since virtio_fs_init() is not
an __exit function.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202402270649.GYjNX0yw-lkp@intel.com/
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>