x86: Eliminate irq_mis_count counted in arch_irq_stat

With the current implementation, kstat_cpu(cpu).irqs_sum is also
increased in case of irq_mis_count increment.

So there is no need to count irq_mis_count in arch_irq_stat,
otherwise irq_mis_count will be counted twice in the sum of
/proc/stat.
Reported-by: Liu Chuansheng <chuansheng.liu@intel.com>
Signed-off-by: Li Fei <fei.li@intel.com>
Acked-by: Liu Chuansheng <chuansheng.liu@intel.com>
Cc: tomoki.sekiyama.qu@hitachi.com
Cc: joe@perches.com
Link: http://lkml.kernel.org/r/1366980611.32469.7.camel@fli24-HP-Compaq-8100-Elite-CMT-PC
Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/irq.c

@@ -165,10 +165,6 @@ u64 arch_irq_stat_cpu(unsigned int cpu)
 u64 arch_irq_stat(void)
 {
 	u64 sum = atomic_read(&irq_err_count);
-
-#ifdef CONFIG_X86_IO_APIC
-	sum += atomic_read(&irq_mis_count);
-#endif
 	return sum;
 }