meta-arm-bsp:linux-linaro-arm: Fix kernel menuconfig task

When calling `bitbake virtual/kernel -c menuconfig` it fails if the
ncurses-dev package is not installed on the host machine.

This patch makes usage of the ncurses library built by yocto if it
is present.

Change-Id: I6a8c4ca6a7da07ac834b29a2d23e83e6c153efb3
Signed-off-by: Diego Sueiro <diego.sueiro@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>