drm/gem: fix not to assign error value to gem name

If idr_alloc() is failed, obj->name can be error value. Also
it cleans up duplicated flink processing code.

This regression has been introduced in

commit 2e928815c1886fe628ed54623aa98d0889cf5509
Author: Tejun Heo <[email protected]>
Date:   Wed Feb 27 17:04:08 2013 -0800

    drm: convert to idr_alloc()

Signed-off-by: YoungJun Cho <[email protected]>
Signed-off-by: Seung-Woo Kim <[email protected]>
Signed-off-by: Kyungmin Park <[email protected]>
Cc: [email protected]
Reviewed-by: Chris Wilson <[email protected]>
Signed-off-by: Dave Airlie <[email protected]>
1 file changed