nir: Add a pass to repair SSA form

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

src/compiler/nir/nir.h

@@ -2235,6 +2235,9 @@ bool nir_ssa_defs_interfere(nir_ssa_def *a, nir_ssa_def *b);
 void nir_convert_to_ssa_impl(nir_function_impl *impl);
 void nir_convert_to_ssa(nir_shader *shader);
 
+bool nir_repair_ssa_impl(nir_function_impl *impl);
+bool nir_repair_ssa(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
  * node) to registers.