xfs: split out attribute fork truncation code into separate file

The attribute inactivation code is not used by userspace, so like
the attribute listing, split it out into a separate file to minimise
the differences between the filesystem shared with libxfs in
userspace.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

diff --cc fs/xfs/Makefile
Simple merge

diff --cc fs/xfs/xfs_attr.c
Simple merge

diff --cc fs/xfs/xfs_attr_inactive.c
Simple merge

diff --cc fs/xfs/xfs_attr_leaf.c
Simple merge