This is a first pass at getting the secureboot patches working with the
upstream lockdown patches that got merged. The final patch from our
lockdown set is the sysrq patch which also needs work. For the present
it is not applied.
Upstream has made a keyring to the platform keys. The "KEYS: Allow
unrestricted boot-time addition of keys to secondary keyring" is
available upstream for the platform keyring.
The only issue is that module signatures aren't checked with the
platform keyring, so this introduces a patch to add that which has been
sent upstream. At least our carried-patch count hasn't gone up.