[IA64] iosapic.c: don't direct interrupts to offline cpus

Ignore offline CPUs when registering IOSAPIC interrupts.  We previously
directed interrupts even to offline CPUs, which means that if you have some
unused CPUs (e.g., you used "maxcpus="), some interrupts won't work.

This really hurts because distro installs typically use "maxcpus=1".

Patch by Alex Williamson.
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/kernel/iosapic.c

@@ -522,6 +522,11 @@ get_target_cpu (unsigned int gsi, int vector)
 
 		cpu_mask = node_to_cpumask(iosapic_lists[iosapic_index].node);
 
+		for_each_cpu_mask(numa_cpu, cpu_mask) {
+			if (!cpu_online(numa_cpu))
+				cpu_clear(numa_cpu, cpu_mask);
+		}
+
 		num_cpus = cpus_weight(cpu_mask);
 
 		if (!num_cpus)