staging: lustre: osc: remove handling cl_avail_grant less than zero

Earlier cl_avail_grant was changed to an unsigned int. Juila
Lawall reported for the upstream client the following which
affects the Intel branch as well:

drivers/staging/lustre/lustre/osc/osc_request.c:1045:5-24: WARNING: Unsigned
expression compared with zero: cli -> cl_avail_grant < 0

Since cl_avail_grant can never be negative we can remove the
code handling the negative value case.

Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Intel-bug-id: LU-8697 https://jira.hpdd.intel.com/browse/LU-6303
Reviewed-on: http://review.whamcloud.com/23155


Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Frank Zago <fzago@cray.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
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>