1. modify cpu.h not include config.h
2. modify u-boot.lds less than 14k for bl2
3. config debug uart2 for dpboard
    modified:   arch/arm/include/asm/arch-exynos/cpu.h
    modified:   board/samsung/exynos4412/Makefile
    modified:   board/samsung/exynos4412/smdk4412_val.h
    modified:   board/samsung/exynos4412/u-boot.lds