ARM: imx_v6_v7_defconfig: enable bpf syscall and cgroup bpf

Enable CONFIG_BPF_SYSCALL and CONFIG_CGROUP_BPF to allow for systemd
interoperability. This avoids the following failure on boot:

[   10.615914] systemd[1]: system-getty.slice: unit configures an IP
 firewall, but the local system does not support BPF/cgroup firewalling.

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>