bpf: rename bpf_ctx_wide_store_ok to bpf_ctx_wide_access_ok

Rename bpf_ctx_wide_store_ok to bpf_ctx_wide_access_ok to indicate
that it can be used for both loads and stores.

Cc: Yonghong Song <yhs@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>