Remove uses of devfs_mk_symlink().

We didn't do this before to avoid breaking most user setups, but this patch
should be quite harmless.

I've excluded the hottest part, i.e.  the ubd symlink, while removing the
other; I released a end-user tree with this patch and there was a good number
of people using the symlink rather than the preferred name.  That part will be
merged later, I think.

Since now we have evidence of less and less users using devfs, we think that
it will not cause too much problems.
Acked-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade_spam@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>