drm/vmwgfx: Annotate ignored return values

Cast return values to void since they, based on input arguments,
are known to be zero.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Reviewed-by: Charmaine Lee <charmainel@vmware.com>
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
index be35385..541a588 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
@@ -1293,7 +1293,7 @@ static void __vmw_svga_enable(struct vmw_private *dev_priv)
  */
 void vmw_svga_enable(struct vmw_private *dev_priv)
 {
-	ttm_read_lock(&dev_priv->reservation_sem, false);
+	(void) ttm_read_lock(&dev_priv->reservation_sem, false);
 	__vmw_svga_enable(dev_priv);
 	ttm_read_unlock(&dev_priv->reservation_sem);
 }