LU-6142 osc: remove oe_next_page

LU-6142 osc: remove oe_next_page

As the comment says, this field is unused.  So remove it.

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.com>
Change-Id: Ibf4ccc9c09c4efcf5c768e71e0fd448958a943f3
Reviewed-on: https://review.whamcloud.com/35890
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.super@gmail.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>