Drivers: hv: vmbus: Specify the target CPU that should receive notification

During the initial VMBUS connect phase, starting with WS2012 R2, we should
specify the VPCU in the guest that should receive the notification. Fix this
issue. This fix is required to properly connect to the host in the kexeced
kernel.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Cc: <stable@vger.kernel.org>        [3.9+]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>