atm: horizon: 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
   9859	    328	      6	  10193	   27d1	drivers/atm/horizon.o

File size After adding 'const':
   text	   data	    bss	    dec	    hex	filename
   9923	    264	      6	  10193	   27d1	drivers/atm/horizon.o
Signed-off-by: NArvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/atm/horizon.c

@@ -2867,7 +2867,7 @@ MODULE_PARM_DESC(max_tx_size, "maximum size of TX AAL5 frames");
 MODULE_PARM_DESC(max_rx_size, "maximum size of RX AAL5 frames");
 MODULE_PARM_DESC(pci_lat, "PCI latency in bus cycles");
 
-static struct pci_device_id hrz_pci_tbl[] = {
+static const struct pci_device_id hrz_pci_tbl[] = {
 	{ PCI_VENDOR_ID_MADGE, PCI_DEVICE_ID_MADGE_HORIZON, PCI_ANY_ID, PCI_ANY_ID,
 	  0, 0, 0 },
 	{ 0, }