tty: mxser: 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
  20253	   1184	  19904	  41341	   a17d	drivers/tty/mxser.o

File size After adding 'const':
   text	   data	    bss	    dec	    hex	filename
  21117	    300	  19904	  41341	   a17d	drivers/tty/mxser.o

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/mxser.c

@@ -145,7 +145,7 @@ static const struct mxser_cardinfo mxser_cards[] = {
 
 /* driver_data correspond to the lines in the structure above
    see also ISA probe function before you change something */
-static struct pci_device_id mxser_pcibrds[] = {
+static const struct pci_device_id mxser_pcibrds[] = {
 	{ PCI_VDEVICE(MOXA, PCI_DEVICE_ID_MOXA_C168),	.driver_data = 3 },
 	{ PCI_VDEVICE(MOXA, PCI_DEVICE_ID_MOXA_C104),	.driver_data = 4 },
 	{ PCI_VDEVICE(MOXA, PCI_DEVICE_ID_MOXA_CP132),	.driver_data = 8 },