pico-imx6: Add initial support

Add the initial support for the pico-imx6 variants.

DDR initialization is based on the TechNexion's U-Boot code.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Fabio Berton <fabio.berton@ossystems.com.br>
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
diff --git a/board/technexion/pico-imx6/README b/board/technexion/pico-imx6/README
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+How to Update U-Boot on pico-imx6q/dl boards
+--------------------------------------------
+
+Required software on the host PC:
+
+- UUU: https://github.com/NXPmicro/mfgtools
+
+Build U-Boot for pico:
+
+$ make mrproper
+$ make pico-imx6_defconfig
+$ make
+
+This generates the SPL and u-boot-dtb.img binaries.
+
+1. Loading U-Boot via USB Serial Download Protocol
+
+Note: This method is convenient for development purposes.
+If the eMMC has already a U-Boot flashed then the user can
+go to step 2 below in order to update U-Boot.
+
+Put pico board in USB download mode (Refer to the following link for details:
+https://www.technexion.com/support/knowledgebase/boot-configuration-settings-for-pico-baseboards/).
+
+Connect a USB to serial adapter between the host PC and pico.
+
+Connect a USB cable between the OTG pico port and the host PC.
+
+Open a terminal program such as minicom.
+
+Copy SPL and u-boot-dtb.img to the uuu folder.
+
+Load the U-Boot via USB:
+
+$ sudo ./uuu -v uuu_script
+
+where uuu_script contains the following:
+
+SDP:  boot -f SPL
+SDPU: write -f u-boot-dtb.img -addr 0x10000000
+SDPU: jump -addr 0x10000000
+
+Then U-Boot starts and its messages appear in the console program.
+
+Use the default environment variables:
+
+=> env default -f -a
+=> saveenv
+
+2. Flashing U-Boot into the eMMC
+
+The  default  U-Boot   environment  expects  the  use   of  eMMC  user
+partition. To ensure we are using  the proper eMMC partition for boot,
+please run:
+
+=> mmc partconf 0 0 0 0
+
+Next, run the DFU agent so we can flash the new images using dfu-util
+tool:
+
+=> dfu 0 mmc 0
+
+Flash SPL and u-boot-dtb.img into the eMMC running the following commands on a PC:
+
+$ sudo dfu-util -D SPL -a spl
+
+$ sudo dfu-util -D u-boot-dtb.img -a u-boot
+
+Remove power from the pico board.
+
+Put pico board into normal boot mode.
+
+Power up the board and the new updated U-Boot should boot from eMMC.