video: fbdev: arkfb: 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
  12511	   1920	      0	  14431	   385f	drivers/video/fbdev/arkfb.o

File size after adding 'const':
   text	   data	    bss	    dec	    hex	filename
  12607	   1824	      0	  14431	   385f	drivers/video/fbdev/arkfb.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/arkfb.c

@@ -1157,7 +1157,7 @@ static int ark_pci_resume (struct pci_dev* dev)
 
 /* List of boards that we are trying to support */
 
-static struct pci_device_id ark_devices[] = {
+static const struct pci_device_id ark_devices[] = {
 	{PCI_DEVICE(0xEDD8, 0xA099)},
 	{0, 0, 0, 0, 0, 0, 0}
 };