staging: lustre: llite: allow setting stripes to specify OSTs

Extend the llite layer to support specifying individual target
OSTs. Support specifying OSTs for regular files only. Directory
support will be implemented later in a separate project. With
this a file could have for example a OST index layout of
2,4,5,9,11. In addition, duplicate indices will be eliminated
automatically. Calculate the max easize by ld_active_tgt_count
instead of ld_tgt_count. However this may introduce problems
when the OSTs are in recovery because non sufficient buffer
may be allocated to store EA.

Signed-off-by: Jian Yu <jian.yu@intel.com>
Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Signed-off-by: James Simmons <uja.ornl@gmail.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4665
Reviewed-on: http://review.whamcloud.com/9383


Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>