drm/i915: Make i915_save/restore_state and intel_i2c_reset take dev_priv

dev_priv is more appropriate since it is used much more in these.

v2: Commit message and keep the local pdev variable. (Joonas Lahtinen)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>