drivers/net/ethernet/atheros/alx: please add device ID for Killer E2400

This small patch is needed to enable the Killer E2400 Ethernet controller.

This patch was originally authored by Ben Pope and has been submitted to <email address hidden>:

http://thread.gmane.org/gmane.linux.network/376851

However, that patch is currently held up by formatting issues in the commit message, hasn't yet been merged into the netdev branch upstream.

As we have an upcoming product that uses the E2400, it would hugely help System76 if Ubuntu could carry this as a "sauce" patch till it is merged upstream.

In particular, it would help System76 if this patch could be included in time to be on the final Ubuntu 15.10/Wily ISO, otherwise our customer restore procedure will require WiFi, wont be able to utilize Ethernet.

Note I've extensively tested this patch with an E2400 Ethernet controller and it seems 100% solid.

Thanks!

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: linux-image-4.2.0-10-generic 4.2.0-10.12 [modified: boot/vmlinuz-4.2.0-10-generic]
ProcVersionSignature: Ubuntu 4.2.0-10.12-generic 4.2.0
Uname: Linux 4.2.0-10-generic x86_64
ApportVersion: 2.18.1-0ubuntu1
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: jderose 1234 F.... pulseaudio
 /dev/snd/controlC1: jderose 1234 F.... pulseaudio
CurrentDesktop: Unity
Date: Tue Sep 22 13:13:25 2015
HibernationDevice: RESUME=UUID=48e949d3-e2d8-4e07-8c68-c3b88b6bc08e
InstallationDate: Installed on 2015-09-22 (0 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Alpha amd64 (20150922)
MachineType: Notebook P7xxDM(-G)
ProcFB: 0 nouveaufb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.2.0-10-generic root=UUID=9837c4d9-2a5d-4782-baf7-2b3e8f56dece ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-4.2.0-10-generic N/A
 linux-backports-modules-4.2.0-10-generic N/A
 linux-firmware 1.148
SourcePackage: linux
UdevLog: Error: [Errno 2] No such file or directory: '/var/log/udev'
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/15/2015
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 1.05.02
dmi.board.asset.tag: Tag 12345
dmi.board.name: P7xxDM(-G)
dmi.board.vendor: Notebook
dmi.board.version: Not Applicable
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: No Enclosure
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr1.05.02:bd09/15/2015:svnNotebook:pnP7xxDM(-G):pvrNotApplicable:rvnNotebook:rnP7xxDM(-G):rvrNotApplicable:cvnNoEnclosure:ct10:cvrN/A:
dmi.product.name: P7xxDM(-G)
dmi.product.version: Not Applicable
dmi.sys.vendor: Notebook