kconfig: fix ncurses headers location

On some distors (eg. latesst openSuSE), the ncurses headers are not
located in the usual location.

Hard-code this location in the kconfig Makefile, as a (temporary?)
workaround.

Reported-by: Simon Gornall <sgornall@apple.com>
[Fix suggested by Simon]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

 reporter_name="Ioannis E. VENETIS"

 reporter_url="http://sourceware.org/ml/crossgcc/2009-11/msg00109.html"

 reporter_comment=""