LU-2150 ost: ost_brw_read() to ptlrpc_free_bulk_nopin()

LU-2150 ost: ost_brw_read() to ptlrpc_free_bulk_nopin()

since a643e38 (LU-2089) OST do not pin pages involved in
BULKs: this is done to prevent get/put on the pages which
were allocated as part of order N (>1) allocation with 0
refcounter. get/put on such a page leads to warning from
the kernel. in the original patch one code path was not
fixed, so this patch completes the change.

also, to prevent confusion, the patch removes couple macros:
ptlrpc_free_bulk() and ptlrpc_prep_bulk_page(). so now the
caller should specify whether ptlrpc should reference pages
or not.

Signed-off-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Change-Id: I8cf5f334e8f7edab0ad37678e1e8af18904a0be6
Reviewed-on: http://review.whamcloud.com/4256
Tested-by: Hudson
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Mike Pershin <tappro@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>