LU-8587 osp: Remove unused osp_max_pages_per_rpc

LU-8587 osp: Remove unused osp_max_pages_per_rpc

It was never added to be seen from proc and in fact it is
completely unused anyway, so just remove it and the
osp_max_pages_per_rpc_seq_show function.

Change-Id: I4d0c582e4d48daff29795e95a7c8fa1f24340766
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Reviewed-on: https://review.whamcloud.com/24572
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>