ANDROID: BACKPORT: KVM: arm64: Make owner ids 32 bits wide

We will soon need more than 8 bits to encode all possible owner ids in
KVM protected mode. To prepare the ground for this, introduce a new type
for owner_ids, and make it a 32bits wide.

Signed-off-by: Quentin Perret <qperret@google.com>
[willdeacon@: Move IDs to header and fix S2MPU host_stage2_set_owner() callback]
Bug: 209580772
Change-Id: I37add42a2d7f34aa110c00fd9569d81db279d765
Signed-off-by: Will Deacon <willdeacon@google.com>