CHROMIUM: qcserial: Add support for Gobi 3000 devices.

BUG=chromium-os:12380
TEST=Adhoc
With a gobi 3000: boot up, ls /dev/ttyUSB*. You ought to see two.

Signed-off-by: Elly Jones <ellyjones@chromium.org>
Signed-off-by: Jason Glasgow <jglasgow@chromium.org>

Original Review URL: http://codereview.chromium.org/6652004
Original Reviewed-on: http://gerrit.chromium.org/gerrit/101
(cherry picked with edits from 1ed6c4db49cd965ed10538525b9f210588a8bd5c)

Change-Id: Ia9066928c870988583fc4eb16ceb197bbf40038a
Reviewed-on: http://gerrit.chromium.org/gerrit/2630
Reviewed-by: Elly Jones <ellyjones@chromium.org>
Tested-by: Jason Glasgow <jglasgow@chromium.org>