minix: fix add link's wrong position calculation

Fix the add link method.  The oosition in the directory was calculated in
wrong way - it had the incorrect shift direction.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Evgeniy Dushistov <dushistov@mail.ru>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: <stable@kernel.org>		[2.6.lots]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>