LU-10994 lov: remove lov_page

LU-10994 lov: remove lov_page

Remove the lov page layer since it does nothing but costs 24 bytes per
page plus pointer chases.

Signed-off-by: John L. Hammond <jhammond@whamcloud.com>
Change-Id: Icd7b4b0041e0fe414a3a4143179f45845177960e
Reviewed-on: https://review.whamcloud.com/47221
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>