[PATCH] hfs: don't dirty unchanged inode

If inode size hasn't changed, don't do anything further in truncate, which
also prevents a dirty inode, what might upset some readonly devices quite
badly.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>