drm/i915: Make hpd arrays big enough to avoid out of bounds access

intel_hpd_irq_handler() walks the passed in hpd[] array assuming it
contains HPD_NUM_PINS elements. Currently that's not true as we don't
specify an explicit size for the arrays when initializing them. Avoid
the out of bounds accesses by specifying the size for the arrays.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>