radeonsi: fix issues with monolithic shaders

radeonsi: fix issues with monolithic shaders

R600_DEBUG=mono has had no effect since:

    commit 1fabb297177069e95ec1bb7053acb32f8ec3e092
    Author: Marek Olšák <marek.olsak@amd.com>
    Date:   Tue Feb 14 22:08:32 2017 +0100

    radeonsi: have separate LS and ES main shader parts in the shader selector

Also, this assertion was failing:
    si_state_shaders.c:1307: si_shader_select_with_key: Assertion
    `!shader->is_optimized' failed.

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>