x86: convert obsolete irq_desc_t typedef to struct irq_desc

Impact: cleanup

Convert the last remaining users.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/kernel/visws_quirks.c b/arch/x86/kernel/visws_quirks.c
index 191a876..31ffc24 100644
--- a/arch/x86/kernel/visws_quirks.c
+++ b/arch/x86/kernel/visws_quirks.c
@@ -578,7 +578,7 @@
 static irqreturn_t piix4_master_intr(int irq, void *dev_id)
 {
 	int realirq;
-	irq_desc_t *desc;
+	struct irq_desc *desc;
 	unsigned long flags;
 
 	spin_lock_irqsave(&i8259A_lock, flags);