Documentation/kbuild/kconfig.txt: 'make listnewconfig' replaces: yes "" | make oldconfig

Signed-off-by: Regid Ichira <regid23@nt1.in>
Acked-by: Rob Landley <rob@landley.net>
[yann.morin.1998@free.fr: fix trailing whitespace, commit subject]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>