drm/i915: Make GEM object create and create from data take dev_priv

Makes all GEM object constructors consistent.

v2: Fix compilation in GVT code.

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> (v1)