nir: Properly invalidate metadata in nir_opt_remove_phis().
Signed-off-by:Kenneth Graunke <kenneth@whitecape.org> Reviewed-by:
Jason Ekstrand <jason.ekstrand@intel.com> Reviewed-by:
Eduardo Lima Mitev <elima@igalia.com> Cc: mesa-stable@lists.freedesktop.org (cherry picked from commit 59bbe268)