Staging: lustre: lnet: Use list_first_entry_or_null

This patch replaces list_empty and list_entry with
list_first_entry_or_null.
Done using coccinelle:

@@
expression e1,e2;
statement S;
@@
- if(!list_empty(...)){
  e2=
- list_entry(e1.next,
+ list_first_entry_or_null(&e1,
  ...);
+ if(e2){
...
}

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>