[IA64] fix iosapic_remove build error for !HOTPLUG

This patch removes the following stupid compile error that happens
when CONFIG_HOTPLUG is not defined on ia64.

     arch/ia64/kernel/built-in.o(.text+0x712): In function `acpi_unregister_ioapic':
     : undefined reference to `iosapic_remove'
Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

include/asm-ia64/iosapic.h

@@ -75,6 +75,8 @@ extern int __devinit iosapic_init (unsigned long address,
 				    unsigned int gsi_base);
 #ifdef CONFIG_HOTPLUG
 extern int iosapic_remove (unsigned int gsi_base);
+#else
+#define iosapic_remove(gsi_base)				(-EINVAL)
 #endif /* CONFIG_HOTPLUG */
 extern int gsi_to_vector (unsigned int gsi);
 extern int gsi_to_irq (unsigned int gsi);
@@ -102,9 +104,7 @@ extern void __devinit map_iosapic_to_node (unsigned int, int);
 #else
 #define iosapic_system_init(pcat_compat)			do { } while (0)
 #define iosapic_init(address,gsi_base)				(-EINVAL)
-#ifdef CONFIG_HOTPLUG
 #define iosapic_remove(gsi_base)				(-ENODEV)
-#endif /* CONFIG_HOTPLUG */
 #define iosapic_register_intr(gsi,polarity,trigger)		(gsi)
 #define iosapic_unregister_intr(irq)				do { } while (0)
 #define iosapic_override_isa_irq(isa_irq,gsi,polarity,trigger)	do { } while (0)