[ARM] Wrap calls to descriptor handlers

This is part of Thomas Gleixner's generic IRQ patch, which converts
ARM to use the generic IRQ subsystem.  Here, we wrap calls to
desc->handler() in an inline function, desc_handle_irq().  This
reduces the size of Thomas' patch since the changes become more
localised.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-pxa/mainstone.c

@@ -72,7 +72,7 @@ static void mainstone_irq_handler(unsigned int irq, struct irqdesc *desc,
 		if (likely(pending)) {
 			irq = MAINSTONE_IRQ(0) + __ffs(pending);
 			desc = irq_desc + irq;
-			desc->handle(irq, desc, regs);
+			desc_handle_irq(irq, desc, regs);
 		}
 		pending = MST_INTSETCLR & mainstone_irq_enabled;
 	} while (pending);