hyper-v: trace vmbus_teardown_gpadl()

Add tracepoint to CHANNELMSG_GPADL_TEARDOWN sender.

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>