i965: Combine both gl_PatchVerticesIn lowering passes.

Until now, we had separate passes for lowering gl_PatchVerticesIn to
a statically known constant (for TES inputs when linked against a TCS),
and a uniform in the other cases.  Annoyingly, one had to be run before
nir_lower_system_values, and the other afterward.  This simplified the
passes, but made life painful for the callers.

This patch combines both into a single pass.  If you give it a non-zero
static count, it uses that.  If you give it Mesa state slots, it turns
it back into a built-in uniform.  Otherwise, it does nothing.

This also moves the i965 uniform lowering out to shared code.

v2: Make token arrays const.

Reviewed-by: Eric Anholt <eric@anholt.net>

src/intel/compiler/brw_nir.h

@@ -144,8 +144,6 @@ void brw_nir_setup_arb_uniforms(void *mem_ctx, nir_shader *shader,
                                 struct gl_program *prog,
                                 struct brw_stage_prog_data *stage_prog_data);
 
-void brw_nir_lower_patch_vertices_in_to_uniform(nir_shader *nir);
-
 void brw_nir_analyze_ubo_ranges(const struct brw_compiler *compiler,
                                 nir_shader *nir,
                                 const struct brw_vs_prog_key *vs_key,