radeonsi: use ready fences on all shaders, not just optimized ones

radeonsi: use ready fences on all shaders, not just optimized ones

There's a race condition between si_shader_select_with_key and
si_bind_XX_shader:

  Thread 1                         Thread 2
  --------                         --------
  si_shader_select_with_key
    begin compiling the first
    variant
    (guarded by sel->mutex)
                                   si_bind_XX_shader
                                     select first_variant by default
                                     as state->current
                                   si_shader_select_with_key
                                     match state->current and early-out

Since thread 2 never takes sel->mutex, it may go on rendering without a
PM4 for that shader, for example.

The solution taken by this patch is to broaden the scope of
shader->optimized_ready to a fence shader->ready that applies to
all shaders. This does not hurt the fast path (if anything it makes
it faster, because we don't explicitly check is_optimized).

It will also allow reducing the scope of sel->mutex locks, but this is
deferred to a later commit for better bisectability.

Fixes dEQP-EGL.functional.sharing.gles2.multithread.simple.buffers.bufferdata_render

Reviewed-by: Marek Olšák <marek.olsak@amd.com>