bpf: make bpf_copy_from_user_task() gpl only

access_process_vm() is exported by EXPORT_SYMBOL_GPL().

Signed-off-by: Kenta Tada <Kenta.Tada@sony.com>
Link: https://lore.kernel.org/r/20220128170906.21154-1-Kenta.Tada@sony.com


Signed-off-by: Alexei Starovoitov <ast@kernel.org>