nir: make nir_opt_remove_phis_impl() static

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>

src/compiler/nir/nir.h

@@ -3206,7 +3206,6 @@ bool nir_opt_move_load_ubo(nir_shader *shader);
 bool nir_opt_peephole_select(nir_shader *shader, unsigned limit,
                              bool indirect_load_ok, bool expensive_alu_ok);
 
-bool nir_opt_remove_phis_impl(nir_function_impl *impl);
 bool nir_opt_remove_phis(nir_shader *shader);
 
 bool nir_opt_shrink_load(nir_shader *shader);

src/compiler/nir/nir_opt_remove_phis.c

@@ -139,7 +139,7 @@ remove_phis_block(nir_block *block, nir_builder *b)
    return progress;
 }
 
-bool
+static bool
 nir_opt_remove_phis_impl(nir_function_impl *impl)
 {
    bool progress = false;