Revert "ci: Remove T820 from CI temporarily"

Revert "ci: Remove T820 from CI temporarily"

This reverts commit 089c8f0b8da86a05bde8359c84085e0b795abf17.

Our office changes are finished and power is now stable in our lab
for T820 CI to run again.

Cc: Daniel Stone <daniels@collabora.com>
Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4057>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4057>