LU-7408 target: declare write for reply data

LU-7408 target: declare write for reply data

declare reply_data at max possible offset - this ensures
enough credits reserved.

Signed-off-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Change-Id: I08466452e1e95b803f316abae777a8c8f4a8626e
Reviewed-on: http://review.whamcloud.com/17086
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>