uboot-phytec

pfla02: Migrate CONFIG_ENV_IS_IN_SPI_FLASH to defconfig

This board is setting CONFIG_ENV_IS_IN_SPI_FLASH in the header rather
than defconfig, fix.

Cc: Stefano Babic <sbabic@denx.de>
Signed-off-by: Tom Rini <trini@konsulko.com>