drm/i915: remove broken intel_pch_has_edp function

Since we set the output type of PCH attached eDP panels to
INTEL_OUTPUT_eDP this function would never return true when it should.
It's been replaced by working functions.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>