drm/i915: Drop WA 16015675438

drm/i915: Drop WA 16015675438

With dynamic load-balancing disabled on the compute side, there's no
reason left to enable WA 16015675438. Drop it from both PVC and DG2.
Note that this can be done because now the driver always set a fixed
partition of EUs during initialization via the ccs_mode configuration.

The flag to GuC is still needed because of 18020744125, so update
the comment accordingly.

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Mateusz Jablonski <mateusz.jablonski@intel.com>
Acked-by: Michal Mrozek <michal.mrozek@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240306144723.1826977-1-lucas.demarchi@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>