KVM: arm64: Bump up the default KVM sanitised debug version to v8p8

Since ID_AA64DFR0_EL1 and ID_DFR0_EL1 are now writable from userspace,
it is safe to bump up the default KVM sanitised debug version to v8p8.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20231003230408.3405722-6-oliver.upton@linux.dev


Signed-off-by: Oliver Upton <oliver.upton@linux.dev>