drm/i915/gen11: Wa_1408615072/Wa_1407596294 should be on GT list

drm/i915/gen11: Wa_1408615072/Wa_1407596294 should be on GT list

The UNSLICE_UNIT_LEVEL_CLKGATE register programmed by this workaround
has 'BUS' style reset, indicating that it does not lose its value on
engine resets.  Furthermore, this register is part of the GT forcewake
domain rather than the RENDER domain, so it should not be impacted by
RCS engine resets.  As such, we should implement this on the GT
workaround list rather than an engine list.

Bspec: 19219
Fixes: 3551ff928744 ("drm/i915/gen11: Moving WAs to rcs_engine_wa_init()")
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230201222831.608281-2-matthew.d.roper@intel.com