drm/i915: call lpt_init_clock_gating on BDW too

Because BDW has WPT, which is equivalent to LPT. This is just like the
CPT/PPT case.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>