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: NMax Kellermann <mk@cm4all.com>
Signed-off-by: NCyrill Gorcunov <gorcunov@gmail.com>
[ mingo@elte.hu: build fix ]
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/smpboot.c

@@ -893,9 +893,11 @@ static int __cpuinit do_boot_cpu(int apicid, int cpu)
 		smpboot_setup_warm_reset_vector(start_ip);
 		/*
 		 * Be paranoid about clearing APIC errors.
-	 	*/
-		apic_write(APIC_ESR, 0);
-		apic_read(APIC_ESR);
+		*/
+		if (APIC_INTEGRATED(apic_version[boot_cpu_physical_apicid])) {
+			apic_write(APIC_ESR, 0);
+			apic_read(APIC_ESR);
+		}
 	}
 
 	/*