irq: Remove unused debug_poll_all_shared_irqs()

commit 74296a8ed added this function for debug purposes, but it was
never used for anything. Remove it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/interrupt.h

@@ -603,12 +603,6 @@ static inline void init_irq_proc(void)
 }
 #endif
 
-#if defined(CONFIG_GENERIC_HARDIRQS) && defined(CONFIG_DEBUG_SHIRQ)
-extern void debug_poll_all_shared_irqs(void);
-#else
-static inline void debug_poll_all_shared_irqs(void) { }
-#endif
-
 struct seq_file;
 int show_interrupts(struct seq_file *p, void *v);