pci: pcie-designware: Remove irq_desc abuse

There is no reason to care about irq_desc in that context, escpecially
as irq_data for that interrupt is retrieved as well.

Use the proper accessor for the msi descriptor

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Jingoo Han <jg1.han@samsung.com>
Cc: Mohit Kumar <mohit.kumar@st.com>
Cc: pci <linux-pci@vger.kernel.org>
Link: http://lkml.kernel.org/r/20140223212736.987803648@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

drivers/pci/host/pcie-designware.c

@@ -294,14 +294,12 @@ static int assign_irq(int no_irqs, struct msi_desc *desc, int *pos)
 static void clear_irq(unsigned int irq)
 {
 	unsigned int pos, nvec;
-	struct irq_desc *desc;
 	struct msi_desc *msi;
 	struct pcie_port *pp;
 	struct irq_data *data = irq_get_irq_data(irq);
 
 	/* get the port structure */
-	desc = irq_to_desc(irq);
-	msi = irq_desc_get_msi_desc(desc);
+	msi = irq_data_get_msi(data);
 	pp = sys_to_pcie(msi->dev->bus->sysdata);
 	if (!pp) {
 		BUG();