x86: ensure copying runstate/time to L1 rather than L2

x86: ensure copying runstate/time to L1 rather than L2

For a HVM domain, if a vcpu is in the nested guest mode,
__raw_copy_to_guest(), __copy_to_guest() and __copy_field_to_guest()
used by update_runstate_area() and update_secondary_system_time() will
copy data to L2 guest rather than the L1 guest.

This commit temporally clears the nested guest flag before all guest
copies in update_runstate_area() and update_secondary_system_time(),
and restores the flag after those guest copy operations.

The flag clear/restore is combined with the existing
smap_policy_change() which is renamed to update_guest_memory_policy().

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>