x86: Speed up the irq_remapped check in hot pathes

irq_2_iommu is in struct irq_cfg, so we can do the irq_remapped check
based on irq_cfg instead of going through a lookup function. That's
especially interesting in the eoi_ioapic_irq() hotpath.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
diff --git a/arch/x86/include/asm/irq_remapping.h b/arch/x86/include/asm/irq_remapping.h
index 8d84150..1c23360 100644
--- a/arch/x86/include/asm/irq_remapping.h
+++ b/arch/x86/include/asm/irq_remapping.h
@@ -24,10 +24,18 @@
 	irte->dest_id = IRTE_DEST(dest);
 	irte->redir_hint = 1;
 }
+static inline bool irq_remapped(struct irq_cfg *cfg)
+{
+	return cfg->irq_2_iommu.iommu != NULL;
+}
 #else
 static void prepare_irte(struct irte *irte, int vector, unsigned int dest)
 {
 }
+static inline bool irq_remapped(struct irq_cfg *cfg)
+{
+	return false;
+}
 #endif
 
 #endif	/* _ASM_X86_IRQ_REMAPPING_H */