timezone: upgrade to 2021a

Release 2021a - 2021-01-24 10:54:57 -0800

  Changes to future timestamps

    South Sudan changes from +03 to +02 on 2021-02-01 at 00:00.
    (Thanks to Steffen Thorsen.)

Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit ed9114df)
Signed-off-by: Steve Sakoman <steve@sakoman.com>