hvf: remove TSC synchronization code because it isn't fully complete

The existing code in QEMU's HVF support to attempt to synchronize TSC
across multiple cores is not sufficient.  TSC value on other cores
can go backwards.  Until implementation is fixed, remove calls to
hv_vm_sync_tsc().  Pass through TSC to guest OS.

Signed-off-by: Cameron Esfahani <dirty@apple.com>
Message-Id: <44c4afd2301b8bf99682b229b0796d84edd6d66f.1574625592.git.dirty@apple.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>