linux-phytec-ti

nfsd: update mtime on truncate

This fixes a failure in xfstests generic/313 because nfs doesn't update
mtime on a truncate.  The protocol requires this to be done implicity
for a size changing setattr.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>