x86/irq_work: Make it depend on APIC

The irq work interrupt vector is only installed when CONFIG_X86_LOCAL_APIC is
enabled, but the interrupt handler is compiled in unconditionally.

Compile the cruft out when the APIC is disabled.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170828064957.691909010@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/include/asm/irq_work.h b/arch/x86/include/asm/irq_work.h
index f706041..ddbb8ea 100644
--- a/arch/x86/include/asm/irq_work.h
+++ b/arch/x86/include/asm/irq_work.h
@@ -3,9 +3,17 @@
 
 #include <asm/cpufeature.h>
 
+#ifdef CONFIG_X86_LOCAL_APIC
 static inline bool arch_irq_work_has_interrupt(void)
 {
 	return boot_cpu_has(X86_FEATURE_APIC);
 }
+extern void arch_irq_work_raise(void);
+#else
+static inline bool arch_irq_work_has_interrupt(void)
+{
+	return false;
+}
+#endif
 
 #endif /* _ASM_IRQ_WORK_H */