staging: lustre: llite: return from ll_adjust_lum() if lump is NULL

staging: lustre: llite: return from ll_adjust_lum() if lump is NULL

No need to check several times if lump is NULL. Just test once and
return 0 if NULL.

Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-9484
Reviewed-on: https://review.whamcloud.com/27126
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>