ARM: dts: imx6: add aristainetos board support

This patch add support for the imx6dl based aristainetos board
with following configuration:

CPU:   Freescale i.MX6DL rev1.1 at 792 MHz
DRAM:  1 GiB
NAND:  512 MiB
MMC:   FSL_SDHC: 0, FSL_SDHC: 1
SF: Detected N25Q128 with page size 256 Bytes, erase size 64 KiB, total 16 MiB

As this board can used with 2 different display types, the
differences between them are extracted into 2 DTS files, and
the common settings are collected in a common file.

Signed-off-by: Heiko Schocher <hs@denx.de>
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>