x86/xen/time: Initialize pv xen time in init_hypervisor_platform()

In every hypervisor except for xen pv time ops are initialized in
init_hypervisor_platform().

Xen PV domains initialize time ops in x86_init.paging.pagetable_init(),
by calling xen_setup_shared_info() which is a poor design, as time is
needed prior to memory allocator.

xen_setup_shared_info() is called from two places: during boot, and
after suspend. Split the content of xen_setup_shared_info() into
three places:

1. add the clock relavent data into new xen pv init_platform vector, and
   set clock ops in there.

2. move xen_setup_vcpu_info_placement() to new xen_pv_guest_late_init()
   call.

3. Re-initializing parts of shared info copy to xen_pv_post_suspend() to
   be symmetric to xen_pv_pre_suspend

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: steven.sistare@oracle.com
Cc: daniel.m.jordan@oracle.com
Cc: linux@armlinux.org.uk
Cc: schwidefsky@de.ibm.com
Cc: heiko.carstens@de.ibm.com
Cc: john.stultz@linaro.org
Cc: sboyd@codeaurora.org
Cc: hpa@zytor.com
Cc: douly.fnst@cn.fujitsu.com
Cc: peterz@infradead.org
Cc: prarit@redhat.com
Cc: feng.tang@intel.com
Cc: pmladek@suse.com
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: linux-s390@vger.kernel.org
Cc: boris.ostrovsky@oracle.com
Cc: jgross@suse.com
Cc: pbonzini@redhat.com
Link: https://lkml.kernel.org/r/20180719205545.16512-13-pasha.tatashin@oracle.com