brw: fix saturate propagation region overlap range

brw: fix saturate propagation region overlap range

Fixes: https://gitlab.freedesktop.org/mesa/mesa/-/commit/947c828d5cbffe9640ac63103a6223112eeff27f
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/7691

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Signed-off-by: Oleksii Bozhenko <oleksii.bozhenko@globallogic.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20206>