Staging: lustre: lproc_osc: Add check on a variable

Variable rc is not tested for negative values and hence a check should
be included. Also, a check for variable val should be introduced.

Signed-off-by: Shivani Bhardwaj <shivanib134@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>