Drivers: hv: make VMBus bus ids persistent

BugLink: http://bugs.launchpad.net/bugs/1650059

Some tools use bus ids to identify devices and they count on the fact
that these ids are persistent across reboot. This may be not true for
VMBus as we use auto incremented counter from alloc_channel() as such
id. Switch to using if_instance from channel offer, this id is supposed
to be persistent.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit b294809d)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/hv/vmbus_drv.c

@@ -961,8 +961,8 @@ int vmbus_device_register(struct hv_device *child_device_obj)
 {
 	int ret = 0;
 
-	dev_set_name(&child_device_obj->device, "vmbus_%d",
-		     child_device_obj->channel->id);
+	dev_set_name(&child_device_obj->device, "vmbus-%pUl",
+		     child_device_obj->channel->offermsg.offer.if_instance.b);
 
 	child_device_obj->device.bus = &hv_bus;
 	child_device_obj->device.parent = &hv_acpi_dev->dev;