arm64: bpf: Only mitigate cBPF programs loaded by unprivileged users

In the Linux kernel, the following vulnerability has been resolved: arm64: bpf: Only mitigate cBPF programs loaded by unprivileged users Support for eBPF programs loaded by unprivileged users is typically disabled. This means only cBPF programs need to be mitigated for BHB. In addition, only mitigate cBPF programs that were loaded by an unprivileged user. Privileged users can also load the same program via eBPF, making the mitigation pointless.