bpftool: fix output for skipping kernel config check

bpftool: fix output for skipping kernel config check

When bpftool feature does not find kernel config
files under default path or wrong format,
do not output CONFIG_XYZ is not set.
Skip kernel config check and continue.

Signed-off-by: Chethan Suresh <chethan.suresh@sony.com>
Signed-off-by: Kenta Tada <Kenta.Tada@sony.com>
Acked-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/r/20230109023742.29657-1-chethan.suresh@sony.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>