nfsd: Set lc_size_chg before ops->proc_layoutcommit

After proc_layoutcommit success, i_size_read(inode) always >= new_size.
Just set lc_size_chg before proc_layoutcommit, if proc_layoutcommit
failed, nfsd will skip the lc_size_chg, so it's no harm.

Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>