Clear IRQ_INPROGRESS as part of "enable_irq()".

It can have gotten set by a stray interrupt if there were
no handlers while the IRQ was disabled, and we shouldn't
confuse other parts (ie this is another safety-net for the
issues that Al Viro brought up about disable_irq() deadlocks
when no handlers exist).

arch/i386/kernel/irq.c

@@ -380,7 +380,7 @@ void enable_irq(unsigned int irq)
 	spin_lock_irqsave(&desc->lock, flags);
 	switch (desc->depth) {
 	case 1: {
-		unsigned int status = desc->status & ~IRQ_DISABLED;
+		unsigned int status = desc->status & ~(IRQ_DISABLED | IRQ_INPROGRESS);
 		desc->status = status;
 		if ((status & (IRQ_PENDING | IRQ_REPLAY)) == IRQ_PENDING) {
 			desc->status = status | IRQ_REPLAY;