iris: Fix doubling of shared local memory (SLM) sizes.

iris: Fix doubling of shared local memory (SLM) sizes.

Commit 67ee9c5f5537fe85357556a4322a07253d13a697 added support for
using the `pipe_compute_state::req_local_mem` field, because Clover
can have a run-time specified size that isn't baked into the shaders.

However, it started adding the static size from the shader to the
dynamic state-supplied size.  The Mesa state tracker fills out
req_local_mem to prog->Base.info.cs.shared_size, which is exactly
what we fill out prog_data->total_shared to be.  Effectively, this
meant that we double-counted the same SLM requirements, doubling
our space requirements.

Fixes a 10% performance regression in Synmark2's OglCSDof test.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7152>