linux-4.19.37: Configure CGROUP_BPF

Configure CONFIG_BPF_SYSCALL and CONFIG_CGROUP_BPF, so that systemd
services can use network filtering options. See
`man systemd.resource-control`.

This should avoid the warnings

    systemd[1]: File /lib/systemd/system/systemd-journald.service:12 configures an IP firewall (IPAddressDeny=any), but the local system does not support B
    systemd[1]: Proceeding WITHOUT firewalling in effect! (This warning is only shown for the first loaded unit using IP firewalling.)

during boot.

CONFIG_BPF_SYSCALL:

Enable the bpf() system call that allows to manipulate eBPF
programs and maps via file descriptors.

CONFIG_CGROUP_BPF:

Allow attaching eBPF programs to a cgroup using the bpf(2)
syscall command BPF_PROG_ATTACH.

In which context these programs are accessed depends on the type
of attachment. For instance, programs that are attached using
BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
inet sockets.

linux-4.19.37-260.bee

@@ -109,9 +109,11 @@ mee_configure() {
 	CONFIG_CGROUP_DEVICE=y
 	CONFIG_CGROUP_CPUACCT=y
 	CONFIG_CGROUP_PERF=y
+	CONFIG_CGROUP_BPF=y
 	CONFIG_CGROUP_DEBUG=y
 	CONFIG_USER_NS=y
 	CONFIG_BLK_DEV_INITRD=y
+	CONFIG_BPF_SYSCALL=y
 	CONFIG_SLAB=y
 	CONFIG_SMP=y
 	CONFIG_GART_IOMMU=y