yocto/linux: Add BPF kernel configuration

The new version of Podman uses BPF for syscall filtering, so add
this fragment as a dependency.

The docker.cfg file in yocto-kernel-cache, as validated by the
containers_kernelcfg_check, is out-of-sync with the actual
kernel config requirements to run Docker/Podman, so disable the
check.

Signed-off-by: Peter Hoyes <peter.hoyes@arm.com>