LU-3319 procfs: Move NRS TBF proc handling to seq_files

With newer kernels moving their proc file system handling
to seq_files this patch migrates the proc handling for NRS
TBF to this new approach.

Change-Id: I121755b611296bf7b9527de65d0e6cf8c4980151
Signed-off-by: James Simmons <uja.ornl@gmail.com>
Reviewed-on: http://review.whamcloud.com/9384
Reviewed-by: Yang Sheng <yang.sheng@intel.com>
Tested-by: Jenkins
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>