irq: sparse irqs, fix #3

fix non-APIC UP build:

 arch/x86/kernel/built-in.o: In function `setup_arch':
 : undefined reference to `pin_map_size'
 arch/x86/kernel/built-in.o: In function `setup_arch':
 : undefined reference to `first_free_entry'
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/setup.c

@@ -1074,8 +1074,10 @@ void __init setup_arch(char **cmdline_p)
 		nr_irqs = 32 * nr_cpu_ids + 224;
 	init_cpu_to_node();
 #endif
+#ifdef CONFIG_X86_IO_APIC
 	pin_map_size = nr_irqs * 2;
 	first_free_entry = nr_irqs;
+#endif
 
 	init_apic_mappings();
 	ioapic_init_mappings();