drm/i915: remove the unnecessary block around display.hpd_irq_setup

The block was added for spin_lock_irqsave flags, but since the locking
was converted to spin_lock_irq variant, the block is no longer needed.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>