imx6: Initial support for SolidRun CuBox-i devices based on i.MX6 processors (i1...

imx6: Initial support for SolidRun CuBox-i devices based on i.MX6 processors (i1, i2, i2eX, and i4Pro).

- Specifications -

CuBox i1:
- SoC: i.MX6 Solo
- Cores: 1
- Memory Size: 512MB
- GPU: GC880
- Wifi/Bluetooth: Optional
- USB 2.0 ports: 2
- Ethernet: 10/100/1000 Mbps

CuBox i2 | i2eX:
- SoC: i.MX6 Dual Lite
- Cores: 2
- Memory Size: 1GB
- GPU: GC2000
- Wifi/Bluetooth: Optional
- USB 2.0 ports: 2
- Ethernet: 10/100/1000 Mbps

CuBox i4Pro | i4x4:
- SoC: i.MX6 Quad
- Cores: 4
- Memory Size: 2/4 GB
- GPU: GC2000
- Wifi/Bluetooth: Build In
- USB 2.0 ports: 2
- Ethernet: 10/100/1000 Mbps

Built-in u-boot requires SPL (secondary program loader) to be present on the SD-card regardless of the image type which will be loaded.
SPL is generated by the u-boot-mx6cuboxi package which is preselected by the target device and can be found in bin/u-boot-mx6cuboxi directory.

Flashing the SPL:
dd if=/dev/zero of=/dev/mmcblk0 bs=1M count=4
dd if=bin/targets/imx6/generic/u-boot-mx6cuboxi/SPL of=/dev/mmcblk0 bs=1K seek=1

Preparing the firmware on the SD-card:
(echo o; echo n; echo p; echo 1; echo ''; echo ''; echo w) | fdisk /dev/mmcblk0
mkfs.ext4 /dev/mmcblk0p1
mount /dev/mmcblk0p1 /mnt
tar -xzf bin/targets/imx6/generic/openwrt-imx6-device-cubox-i-rootfs.tar.gz -C /mnt/
mkdir -p /mnt/boot
cp bin/targets/imx6/generic/{*-uImage,*.dtb,*.scr} /mnt/boot/

Generated u-boot.img needs to be placed on the first partition:
cp bin/targets/imx6/generic/u-boot-mx6cuboxi/u-boot.img /mnt/

To boot from the SD card:

Boot script which sets mmc/dtb parameters and boots the board is automatically sourced.
If this does not work for any reason:
mmc dev 0; load mmc 0:1 $scriptaddr boot/boot.scr; source $scriptaddr

Currently imx6dl-cubox-i.dtb (Dual Lite) and imx6q-cubox-i.dtb (Quad) device trees are available.

Tested on i4Pro, MMC, USB (+ HiD), HDMI and ethernet ports are working.
Wireless and bluetooth are broken ATM. According to SolidRun forums, BCM4329/BCM4330 firmware is used which works fine on older kernels.

Signed-off-by: Vladimir Vid <vladimir.vid@sartura.hr>