The ->gem_free_object never gets called with a NULL pointer, the check
is redundant. Also checking after the upcast allows compilers to elide
it anyway.
Spotted by coverity.
v2: Fix patch subject.
Reviewed-by: David Herrmann <dh.herrmann@gmail.com> Reviewed-by: Ian Romanick <ian.d.romanick@intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>