drm/vboxvideo: drop DRM_MTRR_WC #define

Doesn't apply to upstream kernels since a rather long time.

Reviewed-by: Hans de Goede <[e-mail]>
Acked-by: Sam Ravnborg <[e-mail]>
Signed-off-by: Daniel Vetter <[e-mail]>
Cc: Hans de Goede <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/vboxvideo/vbox_ttm.c

···
 		return ret;
 	}
 
-#ifdef DRM_MTRR_WC
-	vbox->fb_mtrr = drm_mtrr_add(pci_resource_start(dev->pdev, 0),
-				     pci_resource_len(dev->pdev, 0),
-				     DRM_MTRR_WC);
-#else
 	vbox->fb_mtrr = arch_phys_wc_add(pci_resource_start(dev->pdev, 0),
 					 pci_resource_len(dev->pdev, 0));
-#endif
 	return 0;
 }
 
 void vbox_mm_fini(struct vbox_private *vbox)
 {
-#ifdef DRM_MTRR_WC
-	drm_mtrr_del(vbox->fb_mtrr,
-		     pci_resource_start(vbox->ddev.pdev, 0),
-		     pci_resource_len(vbox->ddev.pdev, 0), DRM_MTRR_WC);
-#else
 	arch_phys_wc_del(vbox->fb_mtrr);
-#endif
 	drm_vram_helper_release_mm(&vbox->ddev);
 }