drm/i915: rip out dev_priv->tex_lru_log_granularity

Assigned in setparam, used never.

I didn't bother to dig through the archives to figure out what
this was supposed to do.

Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>