Since we're going to creat the seen set() anyway, we might as well use
it directly. If we don't do this, we see thousands of function calls
with associated overhead on profiles.
(Bitbake rev: 9d43e3279895639ee4899df635f2546c7ee13737)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>