video: fbdev: pm2fb: 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
  11940	    660	     16	  12616	   3148	drivers/video/fbdev/pm2fb.o

File size after adding 'const':
   text	   data	    bss	    dec	    hex	filename
  12068	    532	     16	  12616	   3148	drivers/video/fbdev/pm2fb.o
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Antonino Daplas <adaplas@gmail.com>
Cc: Maik Broemme <mbroemme@libmpq.org>
Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

drivers/video/fbdev/pm2fb.c

@@ -1732,7 +1732,7 @@ static void pm2fb_remove(struct pci_dev *pdev)
 	framebuffer_release(info);
 }
 
-static struct pci_device_id pm2fb_id_table[] = {
+static const struct pci_device_id pm2fb_id_table[] = {
 	{ PCI_VENDOR_ID_TI, PCI_DEVICE_ID_TI_TVP4020,
 	  PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 },
 	{ PCI_VENDOR_ID_3DLABS, PCI_DEVICE_ID_3DLABS_PERMEDIA2,