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>
13 files changed