xen: suspend: use HYPERVISOR_suspend for PVHVM case instead of open coding

static int xen_hvm_suspend(void *data)

{

	int err;

	struct sched_shutdown r = { .reason = SHUTDOWN_suspend };

	int *cancelled = data;

	BUG_ON(!irqs_disabled());

		return err;

	}

	*cancelled = HYPERVISOR_sched_op(SCHEDOP_shutdown, &r);

	/*

	 * This hypercall returns 1 if suspend was cancelled

	 * or the domain was merely checkpointed, and 0 if it

	 * is resuming in a new domain.

	 */

	*cancelled = HYPERVISOR_suspend(0UL);

	xen_hvm_post_suspend(*cancelled);

	gnttab_resume();