KVM: selftests: Add check of CR0.TS in the #NM handler in amx_test

KVM: selftests: Add check of CR0.TS in the #NM handler in amx_test

Be extra paranoid and assert that CR0.TS is clear when verifying the #NM
in the AMX test is due to the expected XFeature Disable error, i.e. that
the #NM isn't due to CR0.TS=1.

Signed-off-by: Mingwei Zhang <mizhang@google.com>
Link: https://lore.kernel.org/r/20230221163655.920289-6-mizhang@google.com
[sean: reword changelog to make it clear this is pure paranoia]
Signed-off-by: Sean Christopherson <seanjc@google.com>