[MIPS] <asm/irq.h> does not need pt_regs anymore.

Signed-off-by: NAtsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: NRalf 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
 
-struct pt_regs;
-
 extern asmlinkage unsigned int do_IRQ(unsigned int irq);
 
 #ifdef CONFIG_MIPS_MT_SMTC