x86/ioapic: Remove unused IO_APIC_irq_trigger() function

The function isn't used since commit:

  5ad274d41c1b ("x86/irq: Remove unused old IOAPIC irqdomain interfaces")

Removing it fixes the following warning when building with clang:

  arch/x86/kernel/apic/io_apic.c:1219:19: error: unused function
      'IO_APIC_irq_trigger' [-Werror,-Wunused-function]

Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Douglas Anderson <dianders@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170522232035.187985-1-mka@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/apic/io_apic.c

@@ -1200,28 +1200,6 @@ EXPORT_SYMBOL(IO_APIC_get_PCI_irq_vector);
 
 static struct irq_chip ioapic_chip, ioapic_ir_chip;
 
-#ifdef CONFIG_X86_32
-static inline int IO_APIC_irq_trigger(int irq)
-{
-	int apic, idx, pin;
-
-	for_each_ioapic_pin(apic, pin) {
-		idx = find_irq_entry(apic, pin, mp_INT);
-		if ((idx != -1) && (irq == pin_2_irq(idx, apic, pin, 0)))
-			return irq_trigger(idx);
-	}
-	/*
-         * nonexistent IRQs are edge default
-         */
-	return 0;
-}
-#else
-static inline int IO_APIC_irq_trigger(int irq)
-{
-	return 1;
-}
-#endif
-
 static void __init setup_IO_APIC_irqs(void)
 {
 	unsigned int ioapic, pin;