kconfig: fix forward dependencies

In case a set of options are conditional to two different paths,
the forward dependencies in these options is wrong, but in the
first path.

Fix by Arnaud Lacombe on linux-kbuild ML:
http://www.spinics.net/lists/linux-kbuild/msg04832.html

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 COPYING