alpha: Fix type compatibility warning for marvel_map_irq

Acked-by: NPhil Carmody <pc+lkml@asdf.org>
Reviewed-and-Tested-by: NMatt Turner <mattst88@gmail.com>
Signed-off-by: NMatt Turner <mattst88@gmail.com>
Signed-off-by: NRichard Henderson <rth@twiddle.net>

arch/alpha/kernel/sys_marvel.c

@@ -317,8 +317,9 @@ marvel_init_irq(void)
 }
 
 static int 
-marvel_map_irq(struct pci_dev *dev, u8 slot, u8 pin)
+marvel_map_irq(const struct pci_dev *cdev, u8 slot, u8 pin)
 {
+	struct pci_dev *dev = (struct pci_dev *)cdev;
 	struct pci_controller *hose = dev->sysdata;
 	struct io7_port *io7_port = hose->sysdata;
 	struct io7 *io7 = io7_port->io7;