BugLink: https://bugs.launchpad.net/bugs/1820868
When dropping the snapdragon flavour from building, one also
must drop it from kernel-versions which controls the udeb
generation.
Fixes: 128e2a3e33d0 "UBUNTU: packaging: arm64: disable building
the snapdragon flavour" Signed-off-by: Stefan Bader <stefan.bader@canonical.com>