x86, NMI: Clean-up default_do_nmi()

Just re-arrange the code a bit to make it easier to follow what is
going on.  Basically un-negating the if-statement and swapping the code
inside the if-statement with code outside.

No functional changes.
Originally-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1294348732-15030-7-git-send-email-dzickus@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/traps.c

@@ -410,26 +410,24 @@ static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
 	raw_spin_lock(&nmi_reason_lock);
 	reason = get_nmi_reason();
 
-	if (!(reason & NMI_REASON_MASK)) {
-		raw_spin_unlock(&nmi_reason_lock);
-		unknown_nmi_error(reason, regs);
-
-		return;
-	}
-
-	/* AK: following checks seem to be broken on modern chipsets. FIXME */
+	if (reason & NMI_REASON_MASK) {
 		if (reason & NMI_REASON_SERR)
 			pci_serr_error(reason, regs);
-	if (reason & NMI_REASON_IOCHK)
+		else if (reason & NMI_REASON_IOCHK)
 			io_check_error(reason, regs);
 #ifdef CONFIG_X86_32
 		/*
-	 * Reassert NMI in case it became active meanwhile
-	 * as it's edge-triggered:
+		 * Reassert NMI in case it became active
+		 * meanwhile as it's edge-triggered:
 		 */
 		reassert_nmi();
 #endif
 		raw_spin_unlock(&nmi_reason_lock);
+		return;
+	}
+	raw_spin_unlock(&nmi_reason_lock);
+
+	unknown_nmi_error(reason, regs);
 }
 
 dotraplinkage notrace __kprobes void