drm/i915/gt: Drop the duplicate icl workaround

The extra w/a was revived in the backmerge that was meant to fix it!

Fixes: 88c90e80 ("Merge drm/drm-next into drm-intel-next-queued")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190710200428.3275-1-chris@chris-wilson.co.uk