isdn: mISDN: netjet: 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
  10941	   1776	     16	  12733	   31bd isdn/hardware/mISDN/netjet.o

File size After adding 'const':
   text	   data	    bss	    dec	    hex	filename
  11005	   1712	     16	  12733	   31bd isdn/hardware/mISDN/netjet.o
Signed-off-by: NArvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/isdn/hardware/mISDN/netjet.c

@@ -1137,7 +1137,7 @@ static void nj_remove(struct pci_dev *pdev)
 /* We cannot select cards with PCI_SUB... IDs, since here are cards with
  * SUB IDs set to PCI_ANY_ID, so we need to match all and reject
  * known other cards which not work with this driver - see probe function */
-static struct pci_device_id nj_pci_ids[] = {
+static const struct pci_device_id nj_pci_ids[] = {
 	{ PCI_VENDOR_ID_TIGERJET, PCI_DEVICE_ID_TIGERJET_300,
 	  PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0},
 	{ }