uboot-phytec

imx6: aristainetos: convert CONFIG_DM_SPI

enable CONFIG_DM_SPI and CONFIG_DM_SPI_FLASH
and get rid of build removal warnings.

define CONFIG_GPIO_ENABLE_SPI_FLASH is not longer
needed, so remove it from config_whitelist.txt

Signed-off-by: Heiko Schocher <hs@denx.de>