nir: Add an optimization pass to remove trivial continues

Reviewed-by: Timothy Arceri <timothy.arceri@collabora.com>

src/compiler/nir/nir.h

@@ -2559,6 +2559,8 @@ bool nir_opt_peephole_select(nir_shader *shader, unsigned limit);
 
 bool nir_opt_remove_phis(nir_shader *shader);
 
+bool nir_opt_trivial_continues(nir_shader *shader);
+
 bool nir_opt_undef(nir_shader *shader);
 
 bool nir_opt_conditional_discard(nir_shader *shader);