porting uboot on a new board(4) start-up code

- arch/arm/cpu/u-boot.lds
   ENTRY(_start)
   SECTIONS
   {
. = 0x00000000;

- arch/arm/lib/vectors.S
   _start:
b reset

- arch/arm/cpu/armv7/start.S
   reset:
bl save_boot_params
   #ifndef CONFIG_SKIP_LOWLEVEL_INIT
bl cpu_init_cp15
bl cpu_init_crit
   #endif
bl _main

   ENTRY(cpu_init_crit)
b lowlevel_init @ go setup pll,mux,memory
   ENDPROC(cpu_init_crit)

- board/samsung/mango100/lowlevel_init.S
   lowlevel_init:
/* setting SRAM */
ldr r0, =S5PC100_SROMC_BASE
/* for UART */
bl uart_asm_init
/* for TZPC */
bl tzpc_asm_init