zink: set PIPE_CAP_MAX_VIEWPORTS

enables ARB_viewport_array

Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8311>

src/gallium/drivers/zink/zink_screen.c

@@ -227,7 +227,7 @@ zink_get_param(struct pipe_screen *pscreen, enum pipe_cap param)
       return PIPE_ENDIAN_NATIVE; /* unsure */
 
    case PIPE_CAP_MAX_VIEWPORTS:
-      return 1; /* TODO: When GS is supported, use screen->info.props.limits.maxViewports */
+      return screen->info.props.limits.maxViewports;
 
    case PIPE_CAP_MIXED_FRAMEBUFFER_SIZES:
       return 1;