Sync the changes of HVM_PARAM_CALLBACK_VIA ABI introduced by
Xen commit <ca5c54b6ff05> (public/hvm: export the HVM_PARAM_CALLBACK_VIA
ABI in the API).
Signed-off-by: NShannon Zhao <shannon.zhao@linaro.org>
Acked-by: NStefano Stabellini <stefano.stabellini@eu.citrix.com>
Tested-by: NJulien Grall <julien.grall@arm.com>