Revert "drm/i915: Unreference object not handle on creation"

This reverts commit 86f100b1.

The kref API requires the handlecount to be initialised to one on object
creation (so that kref_get() doesn't complain upon first use) so the
dalliance in the drivers is required in order to sink the initial
floating reference.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@kernel.org