zonefs: add MODULE_ALIAS_FS

Add MODULE_ALIAS_FS() to load the module automatically when you do "mount
-t zonefs".

Fixes: 8dcc1a9d

 ("fs: New zonefs file system")
Cc: stable <stable@vger.kernel.org> # 5.6+
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: Johannes Thumshirn <jth@kernel.org>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>