imx: board: Add support for the K+P's kp_imx6q_tpc board

This commit provides support for Kieback & Peter GmbH IMX6Q based
TPC board.

U-boot console output:

U-Boot SPL 2018.05-rc1-00005-g631e2d01fd (Apr 04 2018 - 21:16:24 +0200)
Trying to boot from MMC1

U-Boot 2018.05-rc1-00005-g631e2d01fd (Apr 04 2018 - 21:16:24 +0200)

CPU:   Freescale i.MX6Q rev1.5 996 MHz (running at 792 MHz)
CPU:   Extended Commercial temperature grade (-20C to 105C) at 37C
Reset cause: POR
Board: K+P KP_IMX6Q_TPC i.MX6Q
       Watchdog enabled
I2C:   ready
DRAM:  2 GiB
MMC:   FSL_SDHC: 0, FSL_SDHC: 1
Loading Environment from MMC... OK
In:    serial
Out:   serial
Err:   serial
Net:   FEC [PRIME]
Autoboot in 3 seconds