xtensa: add MX irqchip

MX is an interrupt distributor used in some SMP-capable xtensa
configurations.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>
diff --git a/arch/xtensa/include/asm/irq.h b/arch/xtensa/include/asm/irq.h
index 16464f2..7d194d4 100644
--- a/arch/xtensa/include/asm/irq.h
+++ b/arch/xtensa/include/asm/irq.h
@@ -50,5 +50,6 @@
 		unsigned long *out_hwirq, unsigned int *out_type);
 int xtensa_irq_map(struct irq_domain *d, unsigned int irq, irq_hw_number_t hw);
 unsigned xtensa_map_ext_irq(unsigned ext_irq);
+unsigned xtensa_get_ext_irq_no(unsigned irq);
 
 #endif	/* _XTENSA_IRQ_H */