Looking at this function I had no idea what oldfn was, I doubt anyone
else would either without looking up what the caller does. "parentfn"
would seem a more appropriate name so rename it.
(Bitbake rev: fc70ed596703a1aa954223b169d4ad51193a6ec1)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>