arm_reset(void) should not be in arm_common/arm_cpu.c

The following `arm_reset()` code is not valid for the mc1322x so it should be moved or guarded

``` C
__attribute__((naked, noreturn)) void arm_reset(void)
{
    dINT();
    WDTC   = 0x00FFF;
    WDMOD  = 0x03;
    WDFEED = 0xAA;
    WDFEED = 0x55;

    while (1);
}
```
