x86: tsc_adjust: Remove flaky timing test

The subtest labeled, "MSR_IA32_TSC_ADJUST msr adjustment on tsc
write," sometimes fails. The behavior tested is neither architected
nor guaranteed. Running under qemu/kvm, the 'est_delta_time' has been
observed to be as much as an order of magnitude greater than the
expression that is supposed to be its upper bound.

Remove the flaky subtest, and replace it with some invariants that
actually are architecturally guaranteed (as long as IA32_TSC doesn't
wrap around).

Fixes: 5fecf5d8 ("Added tests for ia32_tsc_adjust funtionality.")
Cc: Will Auld <will.auld.intel@gmail.com>
Signed-off-by: Jim Mattson <jmattson@google.com>
Message-Id: <20220127215548.2016946-1-jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>