imx: mx6sabresd/sabreauto runtime setting fdt_file

Detect the SOC and board variant at runtime and change the dtb name,
but not hardcoding the fdt_file env variable.

Take the following patch as a reference.
Íd58699b157df75f1aa0b363ea9c21add21a0c
"mx6cuboxi: Load the correct 'fdtfile' variable"

Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Reviewed-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Stefano Babic <sbabic@denx.de>
5 files changed