fs: udf: udftime: Replace LGPL boilerplate with SPDX identifier

Replace license boilerplate in udftime.c with SPDX identifier for
LGPL-2.0.

Cc: Paul Eggert <eggert@twinsun.com>
Cc: Richard Fontana <rfontana@redhat.com>
Cc: Pali Rohár <pali@kernel.org>
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Reviewed-by: Jilayne Lovejoy <opensource@jilayne.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <20230522005434.22133-3-bagasdotme@gmail.com>