aco: Fix workgroup size calculation.

aco: Fix workgroup size calculation.

Clear the workgroup size for all supported shader stages.
Also, unify the workgroup size calculation accross various places.

As a result, insert_waitcnt can use the proper workgroup size
which means that some waits can be dropped from tessellation
shaders. Also, in cases where the previous calculation was wrong,
we now insert s_barrier instructions.

Totals from affected shaders (GFX10):
Code Size: 340116 -> 338484 (-0.48 %) bytes

Fixes: a8d15ab6daf0a07476e9dfabe513c0f1e0f3bf82
Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4165>