hv: vmbus: fix vmbus_recvpacket_raw() return code

Don't return success if the buffer has not been initialized.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>