xtensa: remove NO_IRQ definitions

These definitions (-1) were correct when used as a hardware IRQ number,
but are incorrect as a mapped IRQ number.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

arch/xtensa/variants/s6000/include/variant/irq.h

@@ -1,7 +1,6 @@
 #ifndef _XTENSA_S6000_IRQ_H
 #define _XTENSA_S6000_IRQ_H
 
-#define NO_IRQ		(-1)
 #define VARIANT_NR_IRQS 8 /* GPIO interrupts */
 
 extern void variant_irq_enable(unsigned int irq);