xen: rename dom0_op to platform_op

The dom0_op hypercall has been renamed to platform_op since Xen 3.2,
which is ancient, and modern upstream Linux kernels cannot run as dom0
and it anymore anyway.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
diff --git a/drivers/xen/acpi.c b/drivers/xen/acpi.c
index 90307c0..6893c79 100644
--- a/drivers/xen/acpi.c
+++ b/drivers/xen/acpi.c
@@ -58,7 +58,7 @@
 		 bits, val_a, val_b))
 		return -1;
 
-	HYPERVISOR_dom0_op(&op);
+	HYPERVISOR_platform_op(&op);
 	return 1;
 }