ARM: 9217/1: add definition of arch_irq_work_raise()

The arm <asm/irq_work.h> does not define arch_irq_work_raise()
so is triggering the following sparse warning. Add a definiton
to fix this:

kernel/irq_work.c:70:13: warning: symbol 'arch_irq_work_raise' was not declared. Should it be static?
arch/arm/kernel/smp.c:582:6: warning: symbol 'arch_irq_work_raise' was not declared. Should it be static?
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

arch/arm/include/asm/irq_work.h

@@ -9,4 +9,6 @@ static inline bool arch_irq_work_has_interrupt(void)
 	return is_smp();
 }
 
+extern void arch_irq_work_raise(void);
+
 #endif /* _ASM_ARM_IRQ_WORK_H */