drm/vmwgfx: Implement screen targets

Add support for the screen target device interface.
Add a getparam parameter and bump minor to signal availability.

Signed-off-by: Sinclair Yeh <syeh@vmware.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_ioctl.c b/drivers/gpu/drm/vmwgfx/vmwgfx_ioctl.c
index 69c8ce23..55940bc 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_ioctl.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ioctl.c
@@ -105,6 +105,10 @@
 	case DRM_VMW_PARAM_MAX_MOB_SIZE:
 		param->value = dev_priv->max_mob_size;
 		break;
+	case DRM_VMW_PARAM_SCREEN_TARGET:
+		param->value =
+			(dev_priv->active_display_unit == vmw_du_screen_target);
+		break;
 	default:
 		DRM_ERROR("Illegal vmwgfx get param request: %d\n",
 			  param->param);