fs: use path_walk in do_path_lookup

Since path_walk sets the total_link_count to 0 and calls link_path_walk, we
can just call path_walk directly.

Signed-off-by: Josef 'Jeff' Sipek <jsipek@cs.sunysb.edu>
Acked-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>