LU-11848 lov: FIEMAP support for PFL and FLR file

LU-11848 lov: FIEMAP support for PFL and FLR file

* use the high 16 bits of fe_device to record the absolute stripe
  number from the beginning we are processing, so that continuous call
  can resume from the stripe specified by it.

Signed-off-by: Bobi Jam <bobijam@whamcloud.com>
Change-Id: Ie519a9361b2d3ae4977ed2ccf925c92065aa9787
Reviewed-on: https://review.whamcloud.com/40766
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>