tools: arch: x86: pull in pvclock headers

Copy over approximately clean versions of the pvclock headers into
tools. Reconcile headers/symbols missing in tools that are unneeded.

Signed-off-by: Oliver Upton <oupton@google.com>
Message-Id: <20210916181555.973085-2-oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>