fs/affs: bugfix: make symbolic links work again

AFFS symbolic links were broken since kernel 2.6.29

Problem was bisected to the following

commit ebd09abb ("vfs: ensure page symlinks are NUL-terminated")
commit 03514685 ("vfs: introduce helper function to safely
NUL-terminate symlinks")

AFFS wasn't setting inode size when reading symbolic link from disk or
creating a new one. Result was zero allocation in pagecache.

ln -s file symlink

ls -lrt

file
symlink ->

This patch adds inode isize information on inode get and symbolic link
addition.

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>