LU-2158 fsfilt: Remove bits from fsfilt_ext3.c/lustre_fsfilt.h

LU-2158 fsfilt: Remove bits from fsfilt_ext3.c/lustre_fsfilt.h

The only remaining dependency needed from the fsfilt_ext3.c for use in
osd-ldiskfs is the fsfilt_ext3_map_inode_pages function. Thus much of
the fsfilt_ext3.c contents have been removed by this commit because
they are no longer used.

Also, since much of the fsfilt_operations structure is not used anymore,
that structure was trimmed to the bare essentials needed by the
osd-ldiskfs layer. The related inline helper functions were also removed.

Change-Id: Ie0f7d428d15862b1b17df140b7152cb0b56ce3be
Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Christopher J. Morrone <morrone2@llnl.gov>
Reviewed-on: http://review.whamcloud.com/4863
Tested-by: Hudson
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>