intel: fix the gen 11 compute shader scratch IDs

intel: fix the gen 11 compute shader scratch IDs

Scratch space allocation is based on the number of threads in the base
configuration, and we only have one base configuration for ICL, with 8
subslices.

This fixes an issue with Aztec on Vulkan in a machine with a
configuration that's not the base. The issue looks like a regression
from b9e93db20896, but it seems things are broken since forever, just
not easily reproducible.

v2: Reimplement it using the subslices variable. Don't touch TGL.

Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4006>