uboot-imx

ARM: k2g: Update board_name u-boot env variable at runtime

Enable CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG to allow "board_name" to
be set depending on the board it is being ran on.

Update findfdt to use this new dynamic board_name value to determine
which dtb should be used.

Signed-off-by: Franklin S Cooper Jr <fcooper@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>