package/pkg-kconfig: fix error string
Current error string speaks only about "fragment" but here we also deal
with Kconfig files, so let's add "file or fragment" instead of "fragment".
Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>