x86: irq: Fix placement of mp_should_keep_irq()

While f3761db164 ("x86, irq: Fix build error caused by
9eabc99a635a77cbf09") addressed the original build problem,
declaration, inline stub, and definition still seem misplaced: It isn't
really IO-APIC related, and it's being used solely in arch/x86/pci/.
This also means stubbing it out when !CONFIG_X86_IO_APIC was at least
questionable.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Link: http://lkml.kernel.org/r/545747BE020000780004436E@mail.emea.novell.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/apic/io_apic.c

@@ -3964,18 +3964,6 @@ int mp_set_gsi_attr(u32 gsi, int trigger, int polarity, int node)
 	return ret;
 }
 
-bool mp_should_keep_irq(struct device *dev)
-{
-	if (dev->power.is_prepared)
-		return true;
-#ifdef	CONFIG_PM_RUNTIME
-	if (dev->power.runtime_status == RPM_SUSPENDING)
-		return true;
-#endif
-
-	return false;
-}
-
 /* Enable IOAPIC early just for system timer */
 void __init pre_init_apic_IRQ0(void)
 {