SMDK6400: Fix some label undefined in build error

Modify Makefile for cpu_init.c and Start.s use some label,this defined
u-boot.lds of arch/arm/cpu/arm1176. But SMDK6400 use the link script
board/samsung/smdk6400/u-boot-nand.lds. So add some label form u-boot.lds
to u-boot-nand.lds

Signed-off-by: Zhong Hongbo <bocui107@gmail.com>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>