FROMGIT: KVM: arm64: Limit the debug architecture to ARMv8.0

Let's not pretend we support anything but ARMv8.0 as far as the
debug architecture is concerned.

Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
(cherry picked from commit 94893fc9
 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git

 next)
Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: I2b39ba4c3d3ea1965fc43ed6c39a2dd32913a022
Bug: 178098380
Test: atest VirtualizationHostTestCases on an EL2-enabled device