LU-3319 procfs: move mdt/mds proc handling to seq_files

LU-3319 procfs: move mdt/mds proc handling to seq_files

With 3.10 linux kernel and above proc handling now only
uses struct seq_files. This patch migrates the mdt/mds
layer proc entries over to using seq_files.

Signed-off-by: James Simmons <uja.ornl@gmail.com>
Change-Id: Icbafdcd2c2fe3959a51dda3f9c715b0ff8d95742
Reviewed-on: http://review.whamcloud.com/8036
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Yang Sheng <yang.sheng@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>