drm/i915: Remove "VLV magic" from irq setup

No clue what this is supposed to achieve. I think it's been there since
the very beginning, so presumably some kind of kludge for very early
silicon. Let's just throw it out.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460382992-28728-2-git-send-email-ville.syrjala@linux.intel.com


Reviewed-by: Imre Deak <imre.deak@intel.com>