x86: do_boot_cpu - check if we have ESR register

Impact: fix APIC IRQ irregularities on certain older boxes

We should touch the APIC ESR register if only we have it.

The patch fixes the problem mentioned by Max Kellermann:

	http://lkml.org/lkml/2008/10/17/147Bisected-by: Max Kellermann <mk@cm4all.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
[ mingo@elte.hu: build fix ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/smpboot.c

@@ -894,9 +894,11 @@ static int __cpuinit do_boot_cpu(int apicid, int cpu)
 		/*
 		 * Be paranoid about clearing APIC errors.
 		*/
+		if (APIC_INTEGRATED(apic_version[boot_cpu_physical_apicid])) {
 			apic_write(APIC_ESR, 0);
 			apic_read(APIC_ESR);
 		}
+	}
 
 	/*
 	 * Starting actual IPI sequence...