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/ia64/kernel/msi_ia64.c

@@ -23,7 +23,7 @@ static int ia64_set_msi_irq_affinity(struct irq_data *idata,
 	if (irq_prepare_move(irq, cpu))
 		return -1;
 
-	__get_cached_msi_msg(idata->msi_desc, &msg);
+	__get_cached_msi_msg(irq_data_get_msi_desc(idata), &msg);
 
 	addr = msg.address_lo;
 	addr &= MSI_ADDR_DEST_ID_MASK;