VMX: Eliminate cr3 save/loading exiting when UG enabled

VMX: Eliminate cr3 save/loading exiting when UG enabled

With the feature of unrestricted guest, there should be no vmexit
be triggered when guest accesses the cr3 in non-paging mode. This
patch will clear the cr3 save/loading bit in vmcs control filed to
eliminate cr3 access vmexit on UG avaliable hardware.

The previous patch (commit c9efe34c119418a5ac776e5d91aeefcce4576518)
did the same thing compare to this one. But it will cause guest fail
to boot up on non-UG hardware which is repoted by Jan and it has been
reverted (commit 1e2bf05ec37cf04b0e01585eae524509179f165e).

This patch incorporate the fixing and guest are working well both in
UG and non-UG platform with this patch.

Reported-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>