mediatek: Add ATF dependency to mediatek u-boot
Mediatek u-boot needs 'bl31' binary to create fip-image. 'bl31' is built by ATF, so ATF needs to be built before u-boot.
Removed dependency to u-boot in ATF to prevent circular dependencies.
Mediatek u-boot needs 'bl31' binary to create fip-image. 'bl31' is built by ATF, so ATF needs to be built before u-boot.
Removed dependency to u-boot in ATF to prevent circular dependencies.