x86/ioapic: Use legacy_pic to set correct gsi-irq mapping

Using compile time NR_LEGACY_IRQS causes the wrong gsi-irq
mapping on non-PC platforms, such as Moorestown. This patch uses
legacy_pic abstraction to set the correct number of legacy
interrupts at runtime. For Moorestown, nr_legacy_irqs = 0. We
have 1:1 mapping for gsi-irq even within the legacy irq range.
Signed-off-by: NJacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: NDirk Brandewie <dirk.brandewie@gmail.com>
Link: http://lkml.kernel.org/n/tip-kzvj4xp9tmicuoqoh2w05iay@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/apic/io_apic.c

@@ -1010,7 +1010,7 @@ static int pin_2_irq(int idx, int apic, int pin)
 	} else {
 		u32 gsi = gsi_cfg->gsi_base + pin;
 
-		if (gsi >= NR_IRQS_LEGACY)
+		if (gsi >= legacy_pic->nr_legacy_irqs)
 			irq = gsi;
 		else
 			irq = gsi_top + gsi;
@@ -3610,7 +3610,7 @@ static void __init probe_nr_irqs_gsi(void)
 {
 	int nr;
 
-	nr = gsi_top + NR_IRQS_LEGACY;
+	nr = gsi_top + legacy_pic->nr_legacy_irqs;
 	if (nr > nr_irqs_gsi)
 		nr_irqs_gsi = nr;