x86: fix HPET compiler error when not using CONFIG_PCI_MSI

Added dummy function for hpet_setup_msi_irq().
Signed-off-by: Steven Noonan <steven@uplinklabs.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/hpet.c

@@ -635,6 +635,10 @@ static int hpet_cpuhp_notify(struct notifier_block *n,
 }
 #else
 
+static int hpet_setup_msi_irq(unsigned int irq)
+{
+	return 0;
+}
 void hpet_msi_capability_lookup(unsigned int start_timer)
 {
 	return;