Staging: most: cdev: Remove useless check

The variable mbo is already NULL tested so, check on it should be
removed.
Semantic patch used:

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

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