drm/i915: don't implement WaDisableEarlyCull for Haswell

Introduced in commit 87f8020e:
  drm/i915: implement WaDisableEarlyCull for VLV and IVB

Notice that the original patch sent to the mailing list did not
include the Haswell chunk, it was added later.

The bit set by the commit does not exist on Haswell machines (at least
that's what the documentation says). Also, the commit gives me a GPU
hang every time we're loading the driver. So let's revert the Haswell
chunk, making the patch do only what its title actually says.

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>