glsl/nir: Add and use a gl_nir_link() function

Perform all the NIR linking steps in order.  Change iris and i965 to
use it.  Suggested by Alejandro.

v2: Add gl_nir_linker_options struct.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com> [v1]

src/compiler/glsl/gl_nir_linker.h

@@ -31,6 +31,14 @@ extern "C" {
 struct gl_context;
 struct gl_shader_program;
 
+struct gl_nir_linker_options {
+   bool fill_parameters;
+};
+
+bool gl_nir_link(struct gl_context *ctx,
+                 struct gl_shader_program *prog,
+                 const struct gl_nir_linker_options *options);
+
 bool gl_nir_link_uniforms(struct gl_context *ctx,
                           struct gl_shader_program *prog,
                           bool fill_parameters);