drm/i915: merge the two hpd loops in intel_hpd_irq_handler to one

Nothing in the two consecutive loops over hpd pins depends on state in a
larger context than the single hpd pin. If we skip the rest of the loop
on short hpd pulses, we can merge the two loops into one.

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>