fs_parser: update mount_api doc to match function signature

fs_parser: update mount_api doc to match function signature

Add the missing 'name' parameter to the mount_api documentation for
fs_validate_description().

Fixes: 96cafb9ccb15 ("fs_parser: remove fs_parameter_description name field")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20241125215021.231758-1-rdunlap@infradead.org
Cc: Eric Sandeen <sandeen@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>