infiniband: mthca: 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
  13067	    805	      4	  13876	   3634	infiniband/hw/mthca/mthca_main.o

File size After adding 'const':
   text	   data	    bss	    dec	    hex	filename
  13419	    453	      4	  13876	   3634	infiniband/hw/mthca/mthca_main.o

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/mthca/mthca_main.c

@@ -1162,7 +1162,7 @@ static void mthca_remove_one(struct pci_dev *pdev)
 	mutex_unlock(&mthca_device_mutex);
 }
 
-static struct pci_device_id mthca_pci_table[] = {
+static const struct pci_device_id mthca_pci_table[] = {
 	{ PCI_DEVICE(PCI_VENDOR_ID_MELLANOX, PCI_DEVICE_ID_MELLANOX_TAVOR),
 	  .driver_data = TAVOR },
 	{ PCI_DEVICE(PCI_VENDOR_ID_TOPSPIN, PCI_DEVICE_ID_MELLANOX_TAVOR),