x86/vmx: add hvm functions to get/set non-register state

x86/vmx: add hvm functions to get/set non-register state

During VM forking and resetting a failed vmentry has been observed due
to the guest non-register state going out-of-sync with the guest register
state. For example, a VM fork reset right after a STI instruction can trigger
the failed entry. This is due to the guest non-register state not being saved
from the parent VM, thus the reset operation only copies the register state.

Fix this by adding a new pair of hvm functions to get/set the guest
non-register state so that the overall vCPU state remains in sync.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Acked-by: Jan Beulich <jbeulich@suse.com>