staging: lustre: fix 'no effect' errors

Fix 'no effect' issues found by Coverity version 6.5.1:

Unsigned compared against 0 (NO_EFFECT)
This greater-than-or-equal-to-zero comparison of an unsigned value
is always true.

Remove useless cast.

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3907
Reviewed-on: http://review.whamcloud.com/7166


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>