Staging: lustre: llite_lib: Remove unnecessary NULL check

Variable op_data is already tested for NULL value and therefore any
further checks should be removed.
Semantic patch used:

@@ expression E;@@
if(E==NULL) {... return ...;}
- if(E){
  ...
- }

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