[PATCH] reiserfs: make resize option auto-get new device size

It's trivial for the resize option to auto-get the underlying device size,
while it's harder for the user.  I've copied the code from jfs.

Since of the different reiserfs option parser (which does not use the
superior match_token used by almost every other filesystem), I've had to
use the "resize=auto" and not "resize" option to specify this behaviour.
Changing the option parser to the kernel one wouldn't be bad but I've no
time to do this cleanup in this moment.

Btw, the mount(8) man page should be updated to include this option.  Cc
the relevant people, please (I hope I cc'ed the right people).

Cc: <reiserfs-dev@namesys.com>
Cc: <reiserfs-list@namesys.com>
Cc: <mtk-manpages@gmx.net>
Cc: Alex Zarochentsev <zam@namesys.com>
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>