isdn: hisax: constify pci_device_id.

pci_device_id are not supposed to change at runtime. All functions
working with pci_device_id provided by <linux/pci.h> work with
const pci_device_id. So mark the non-const structs as const.

File size before:
   text	   data	    bss	    dec	    hex	filename
  13686	   2064	   4416	  20166	   4ec6	drivers/isdn/hisax/config.o

File size After adding 'const':
   text	   data	    bss	    dec	    hex	filename
  15030	    720	   4416	  20166	   4ec6	drivers/isdn/hisax/config.o
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/isdn/hisax/config.c

@@ -1909,7 +1909,7 @@ static void EChannel_proc_rcv(struct hisax_d_if *d_if)
 #ifdef CONFIG_PCI
 #include <linux/pci.h>
 
-static struct pci_device_id hisax_pci_tbl[] __used = {
+static const struct pci_device_id hisax_pci_tbl[] __used = {
 #ifdef CONFIG_HISAX_FRITZPCI
 	{PCI_VDEVICE(AVM,      PCI_DEVICE_ID_AVM_A1)			},
 #endif