After all, we call ibx_irq_preinstall from gen8_irq_preinstall.

v2: - Rebase.
Reviewed-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>