ksmbd: remove unused ksmbd_tree_conn_share function

Remove unused ksmbd_tree_conn_share function.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
