drm/i915: Use dev_priv instead of dev in irq setup functions

It's the new world order!

Not going full monty on these here and rolling this out throughout the
subsequent call chains since this is just for the kerneldoc. Later on
we can go more crazy, especially once we've embedded drm_device
correctly.

v2: Also frob the runtime_pm functions ...

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>