linux-yocto-tiny-kexecboot: do not exec do_package_qa task

The task was added with commit d31f75a72cb2322f753d945da86d5f3287eef06b
"insane: Split do_package_qa into a separate task (from do_package)"
and we avoid it because the recipe does not create packages.

Signed-off-by: Andrea Adami <andrea.adami@gmail.com>