GKI repurposes module signing to distinguish GKI and vendor modules.
It was unhelpful and sometimes confusing to taint the kernel when
loading vendor modules.
Bug: 232430739
Bug: 383260800
Change-Id: If05a9e7d8e28954eba0472149fe312045c9c4fad
Signed-off-by: Giuliano Procida <gprocida@google.com>