configs: add defconfig for TS-7680

configs: add defconfig for TS-7680

The TS-7680 is an i.MX286 ARM ARM926EJ-S board with 10/100 Ethernet,
USB port, eMMC and CAN ports.

The TS-7680 uses a 3.14.28 Linux kernel provided by Technologic Systems:
https://github.com/embeddedarm/linux-3.14.28-imx28

U-Boot is not provided as the manufacturer recommends not to update the
built-in bootloader.

For more informations please see:
https://wiki.embeddedarm.com/wiki/TS-7680

Signed-off-by: Julien Grossholtz <julien.grossholtz@savoirfairelinux.com>
[Thomas: use same headers as the kernel being built, update .gitlab-ci.yml.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>