arm: imx: add i.MX6ULL 14x14 EVK board support

Add i.MX6ULL EVK board support:
Add device tree file, which is copied from NXP Linux.
Enabled DM_MMC, DM_GPIO, DM_I2C, DM_SPI, PINCTRL, DM_REGULATOR.
The uart iomux settings are still keeped in board file.

Boot Log:
U-Boot 2016.09-rc1-00366-gbb419ef-dirty (Aug 11 2016 - 13:08:58 +0800)

CPU:   Freescale i.MX6ULL rev1.0 at 396MHz
CPU:   Commercial temperature grade (0C to 95C) at 15C
Reset cause: POR
Model: Freescale i.MX6 ULL 14x14 EVK Board
Board: MX6ULL 14x14 EVK
DRAM:  512 MiB
MMC:   initialized IMX pinctrl driver
FSL_SDHC: 0, FSL_SDHC: 1
In:    serial
Out:   serial
Err:   serial
Net:   CPU Net Initialization Failed
No ethernet found.
Hit any key to stop autoboot:  0
=> mmc dev 1
switch to partitions #0, OK
mmc1 is current device

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>