drm/vmwgfx: 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
  13765	    800	     20	  14585	   38f9	gpu/drm/vmwgfx/vmwgfx_drv.o

File size After adding 'const':
   text	   data	    bss	    dec	    hex	filename
  13829	    736	     20	  14585	   38f9	gpu/drm/vmwgfx/vmwgfx_drv.o

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>

drivers/gpu/drm/vmwgfx/vmwgfx_drv.c

@@ -227,7 +227,7 @@ static const struct drm_ioctl_desc vmw_ioctls[] = {
 		      DRM_AUTH | DRM_RENDER_ALLOW),
 };
 
-static struct pci_device_id vmw_pci_id_list[] = {
+static const struct pci_device_id vmw_pci_id_list[] = {
 	{0x15ad, 0x0405, PCI_ANY_ID, PCI_ANY_ID, 0, 0, VMWGFX_CHIP_SVGAII},
 	{0, 0, 0}
 };