nir: make nir_to_lcssa() a general NIR pass.

Reviewed-by: Connor Abbott <cwabbott0@gmail.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/compiler/nir/nir.h

@@ -3923,6 +3923,7 @@ bool nir_repair_ssa_impl(nir_function_impl *impl);
 bool nir_repair_ssa(nir_shader *shader);
 
 void nir_convert_loop_to_lcssa(nir_loop *loop);
+bool nir_convert_to_lcssa(nir_shader *shader);
 
 /* If phi_webs_only is true, only convert SSA values involved in phi nodes to
  * registers.  If false, convert all values (even those not involved in a phi