[MIPS] do_IRQ cleanup

Now we have both function and macro version of do_IRQ() and the former
is used only by DEC and non-preemptive kernel.  This patch makes
everyone use the macro version and removes the function version.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

include/asm-mips/irq.h

@@ -24,8 +24,6 @@ static inline int irq_canonicalize(int irq)
 #define irq_canonicalize(irq) (irq)	/* Sane hardware, sane code ... */
 #endif
 
-extern asmlinkage unsigned int do_IRQ(unsigned int irq);
-
 #ifdef CONFIG_MIPS_MT_SMTC
 /*
  * Clear interrupt mask handling "backstop" if irq_hwmask
@@ -43,8 +41,6 @@ do {									\
 #define __DO_IRQ_SMTC_HOOK() do { } while (0)
 #endif
 
-#ifdef CONFIG_PREEMPT
-
 /*
  * do_IRQ handles all normal device IRQ's (the special
  * SMP cross-CPU interrupts have their own specific
@@ -61,8 +57,6 @@ do {									\
 	irq_exit();							\
 } while (0)
 
-#endif
-
 extern void arch_init_irq(void);
 extern void spurious_interrupt(void);