Staging: lustre: Use list_{next/prev}_entry instead of list_entry

This patch replace list_entry with list_{next/prev}_entry as it makes
the code more clear to read.
Done using coccinelle:

@@
expression e1;
identifier e3;
type t;
@@
(
- list_entry(e1->e3.next,t,e3)
+ list_next_entry(e1,e3)
|
- list_entry(e1->e3.prev,t,e3)
+ list_prev_entry(e1,e3)
)

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