packaging-updates-upstream-linux: also check for mainline updates if Apertis...

packaging-updates-upstream-linux: also check for mainline updates if Apertis kernel >= Debian kernel

We should also check for kernel.org updates when Debian provides
kernel of a series since Debian can stop tracking a series that
we still use in Apertis.

Currently, Debian has stopped providing linux 6.6.x, so Apertis
is ahead of Debian by using linux from kernel.org, in this case
we cannot rely on Debian for 6.6.x updates then we have to track
directly kernel.org.

This change fixes a bug that was never noticed before, because
the main users of the dashboard are baseline maintainers who
are usually different than our kernel maintainer.

Signed-off-by: Dylan Aïssi <dylan.aissi@collabora.com>