alpha: silence 'const' warning in sys_marvel.c

warning: passing argument 1 of 'pci_find_capability' discards 'const' qualifier from pointer target type
Signed-off-by: NMatt Turner <mattst88@gmail.com>

arch/alpha/kernel/sys_marvel.c

@@ -317,7 +317,7 @@ marvel_init_irq(void)
 }
 
 static int 
-marvel_map_irq(const struct pci_dev *dev, u8 slot, u8 pin)
+marvel_map_irq(struct pci_dev *dev, u8 slot, u8 pin)
 {
 	struct pci_controller *hose = dev->sysdata;
 	struct io7_port *io7_port = hose->sysdata;