LU-5200 llite: Cmp of unsigned value against 0 is always true

LU-5200 llite: Cmp of unsigned value against 0 is always true

Comparison of unsigned value against 0 is always true.
desc->bd_iov_count declared as int and atomic_sub_return() have
first argument int also.

Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Change-Id: I89cedc4991d1a117f824ce6b5d8cf045595fdc0f
Reviewed-on: http://review.whamcloud.com/11217
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>