broadcom/vc4: Ignore PIPE_BIND_DISPLAY_TARGET in is_format_supported().

We were failing the retval == usage check at the end.

Fixes: f7604d8af5 ("st/dri: only expose config formats that are display targets")

src/gallium/drivers/vc4/vc4_screen.c

@@ -550,6 +550,8 @@ vc4_screen_is_format_supported(struct pipe_screen *pscreen,
                 retval |= PIPE_BIND_INDEX_BUFFER;
         }
 
+        retval |= usage & PIPE_BIND_DISPLAY_TARGET;
+
 #if 0
         if (retval != usage) {
                 fprintf(stderr,