nir: return progress from lower_idiv

With algebraic-opt support for lowering div to shift, the driver would
like to be able to run this pass *after* the main opt-loop, and then
conditionally re-run the opt-loop if this pass actually lowered some-
thing.

Signed-off-by: Rob Clark <robclark@freedesktop.org>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/compiler/nir/nir.h

@@ -2379,7 +2379,7 @@ typedef struct nir_lower_tex_options {
 bool nir_lower_tex(nir_shader *shader,
                    const nir_lower_tex_options *options);
 
-void nir_lower_idiv(nir_shader *shader);
+bool nir_lower_idiv(nir_shader *shader);
 
 void nir_lower_clip_vs(nir_shader *shader, unsigned ucp_enables);
 void nir_lower_clip_fs(nir_shader *shader, unsigned ucp_enables);