treewide: Use helper function to access irq_data->msi_desc

Use irq_data access helper to access irq_data->msi_desc, so we can
move msi_desc from struct irq_data into struct irq_common_data later.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/tile/kernel/pci_gx.c

@@ -1442,7 +1442,7 @@ static struct pci_ops tile_cfg_ops = {
 /* MSI support starts here. */
 static unsigned int tilegx_msi_startup(struct irq_data *d)
 {
-	if (d->msi_desc)
+	if (irq_data_get_msi_desc(d))
 		pci_msi_unmask_irq(d);
 
 	return 0;