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="Yann E. MORIN"

 reporter_url="http://ymorin.is-a-geek.org/projects/crosstool"

 reporter_comment="EXPERIMENTAL MIPS-64 n64 toolchain."