x86/io_apic: Remove unused function mp_init_irq_at_boot()

There are no callers in-tree anymore since

  ef9e56d8 ("x86/ioapic: Remove obsolete post hotplug update")

so remove it.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200508140808.49428-1-yuehaibing@huawei.com

arch/x86/kernel/apic/io_apic.c

@@ -154,19 +154,6 @@ static inline bool mp_is_legacy_irq(int irq)
 	return irq >= 0 && irq < nr_legacy_irqs();
 }
 
-/*
- * Initialize all legacy IRQs and all pins on the first IOAPIC
- * if we have legacy interrupt controller. Kernel boot option "pirq="
- * may rely on non-legacy pins on the first IOAPIC.
- */
-static inline int mp_init_irq_at_boot(int ioapic, int irq)
-{
-	if (!nr_legacy_irqs())
-		return 0;
-
-	return ioapic == 0 || mp_is_legacy_irq(irq);
-}
-
 static inline struct irq_domain *mp_ioapic_irqdomain(int ioapic)
 {
 	return ioapics[ioapic].irqdomain;