package: Drop var-undefined QA check

package: Drop var-undefined QA check

The variables checked for are mandatory in all cases so a QA check does
not seem to be the right choice for this. Additionally, the code never
called `exit_if_errors` so the reported QA issue didn't actually fail
the task.

Signed-off-by: Philip Lorenz <philip.lorenz@bmw.de>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>