LU-6142 lustre: use list_first/last_entry() for list heads

LU-6142 lustre: use list_first/last_entry() for list heads

This patch changes
    list_entry(foo.next, ...)
to
    list_first_entry(&foo, ...)
and
    list_entry(foo.prev, ...)
to
    list_last_entry(&foo, ...)

in cases where 'foo' is a list head - not a list member.

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I22b1278f5b481ce3074db3e59d37d9148016aed5
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/50828
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>