drm/i915: Unreference object not handle on creation

drm/i915: Unreference object not handle on creation

When creating an object, we create the handle by which it is known to
the process and which own the reference to the object. That reference to
the new handle is what we want to transfer to the process, not the lost
reference to the object; so free the local object reference *not* the
process's handle reference.

This brings i915_gem_object_create_ioctl() into line with
drm_gem_open_ioctl()

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Eric Anholt <eric@anholt.net>