mini2440时钟
ldr r0, =0x4c000000
ldr r1, =0xffffffff
str r1, [r0]
ldr r0, =0x4c000014
mov r1, #0x05
str r1, [r0]
mrc p15, 0, r1, c1, c0, 0
orr r1, r1, #0xc0000000
mcr p15, 0, r1, c1, c0, 0
ldr r0, =0x4c000004
ldr r1, =0x5c011
str r1, [r0]
