net: sierra_net: device IDs for Aircard 320U++

Adding device IDs for Aircard 320U and two other devices
found in the out-of-tree version of this driver.

Cc: linux@sierrawireless.com
Cc: Autif Khan <autif.mlist@gmail.com>
Cc: Tom Cassidy <tomas.cassidy@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>