drm: Remove obsolete "This is gross" comment

Remove obsolete comment which was initially added in 2008 to annotate
that idr_find() was used before idr_remove() since idr_remove() didn't
use to return feedback. The comment now is irrelevant with
commit f6cd7daecf ("drm: Release driver references to handle before
making it available again").

Signed-off-by: Haneen Mohammed <hamohammed.sa@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20170921210424.GA21951@Haneen

drivers/gpu/drm/drm_gem.c

@@ -281,15 +281,6 @@ drm_gem_handle_delete(struct drm_file *filp, u32 handle)
 {
 	struct drm_gem_object *obj;
 
-	/* This is gross. The idr system doesn't let us try a delete and
-	 * return an error code.  It just spews if you fail at deleting.
-	 * So, we have to grab a lock around finding the object and then
-	 * doing the delete on it and dropping the refcount, or the user
-	 * could race us to double-decrement the refcount and cause a
-	 * use-after-free later.  Given the frequency of our handle lookups,
-	 * we may want to use ida for number allocation and a hash table
-	 * for the pointers, anyway.
-	 */
 	spin_lock(&filp->table_lock);
 
 	/* Check if we currently have a reference on the object */