DRM/i915: Remove valleyview_hpd_irq_setup.

It's basically identical to i915_hpd_irq_setup().

Signed-off-by: Egbert Eich <eich@suse.de>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>