MIPS: reserve exception vector space ONLY ONCE

"cpu_probe" is called both by BP and APs, but reserving exception vector
(like 0x0-0x1000) called by "cpu_probe" need once and calling on APs is
too late since memblock is unavailable at that time.

So, reserve exception vector ONLY by BP.
Suggested-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Huang Pei <huangpei@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/kernel/traps.c

@@ -2007,7 +2007,13 @@ unsigned long vi_handlers[64];
 
 void reserve_exception_space(phys_addr_t addr, unsigned long size)
 {
-	memblock_reserve(addr, size);
+	/*
+	 * reserve exception space on CPUs other than CPU0
+	 * is too late, since memblock is unavailable when APs
+	 * up
+	 */
+	if (smp_processor_id() == 0)
+		memblock_reserve(addr, size);
 }
 
 void __init *set_except_vector(int n, void *addr)