drm/i915/bxt: clear hpd status sticky bits earlier

The hotplug status is cached in hp_control, and will be passed on to
bottom halves through intel_hpd_irq_handler(), so we can clear the
sticky bits earlier.

While at it, drop the redundant logging of the hotplug status, which
will also be logged by pch_get_hpd_pins().

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>