MIPS: BCM63XX: don't write to the chipid register on reboot

While harmless, it is bad style to do so.

Signed-off-by: Maxime Bizon <mbizon@freebox.fr>
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Patchwork: http://patchwork.linux-mips.org/patch/4092/
Signed-off-by: John Crispin <blogic@openwrt.org>

arch/mips/bcm63xx/setup.c

@@ -86,6 +86,9 @@ void bcm63xx_machine_reboot(void)
 	}
 
 	for (i = 0; i < 2; i++) {
+		if (!perf_regs[i])
+			break;
+
 		reg = bcm_perf_readl(perf_regs[i]);
 		if (BCMCPU_IS_6348()) {
 			reg &= ~EXTIRQ_CFG_MASK_ALL_6348;