staging: lustre: llite: speedup in unlink/rmdir

Assume dchild argument is fully initialized in ->unlink and
->rmdir callbacks, so additional lookup for ELC is not needed.

Signed-off-by: Andrew Perepechko <andrew_perepechko@xyratex.com>
Reviewed-by: Alexander Boyko <Alexander_Boyko@xyratex.com>
Reviewed-by: Vitaly Fertman <Vitaly_Fertman@xyratex.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3473
Xyratex-bug-id: MRP-1027
Reviewed-on: http://review.whamcloud.com/6648


Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>