x86/irq: Rename VECTOR_UNDEFINED to VECTOR_UNUSED

VECTOR_UNDEFINED is a misnomer. The vector is defined, but unused.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Link: http://lkml.kernel.org/r/20150802203609.477282494@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/include/asm/hw_irq.h b/arch/x86/include/asm/hw_irq.h
index 6615032..62bb8d2 100644
--- a/arch/x86/include/asm/hw_irq.h
+++ b/arch/x86/include/asm/hw_irq.h
@@ -182,7 +182,7 @@
 #define trace_irq_entries_start irq_entries_start
 #endif
 
-#define VECTOR_UNDEFINED	(-1)
+#define VECTOR_UNUSED		(-1)
 #define VECTOR_RETRIGGERED	(-2)
 
 typedef int vector_irq_t[NR_VECTORS];