gallium: plumb context priority through to driver

Signed-off-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Andres Rodriguez <andresx7@gmail.com>
Reviewed-by: Wladimir J. van der Laan <laanwj@gmail.com>

src/gallium/drivers/softpipe/sp_screen.c

@@ -315,6 +315,7 @@ softpipe_get_param(struct pipe_screen *screen, enum pipe_cap param)
    case PIPE_CAP_TILE_RASTER_ORDER:
    case PIPE_CAP_MAX_COMBINED_SHADER_OUTPUT_RESOURCES:
    case PIPE_CAP_SIGNED_VERTEX_BUFFER_OFFSET:
+   case PIPE_CAP_CONTEXT_PRIORITY_MASK:
       return 0;
    case PIPE_CAP_SHADER_BUFFER_OFFSET_ALIGNMENT:
       return 4;