staging: lustre: lov: avoid infinite loop in lsm_alloc_plain()

staging: lustre: lov: avoid infinite loop in lsm_alloc_plain()

In lsm_alloc_plain() use a signed loop index to avoid an infinite loop
in the error path.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-6872
Reviewed-on: http://review.whamcloud.com/15644
Reviewed-by: Dmitry Eremin <dmitry.eremin@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>