bpf: add _impl suffix for bpf_stream_vprintk() kfunc

bpf: add _impl suffix for bpf_stream_vprintk() kfunc

Rename bpf_stream_vprintk() to bpf_stream_vprintk_impl().

This makes bpf_stream_vprintk() follow the already established "_impl"
suffix-based naming convention for kfuncs with the bpf_prog_aux
argument provided by the verifier implicitly. This convention will be
taken advantage of with the upcoming KF_IMPLICIT_ARGS feature to
preserve backwards compatibility to BPF programs.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Link: https://lore.kernel.org/r/20251104-implv2-v3-2-4772b9ae0e06@meta.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Ihor Solodrai <ihor.solodrai@linux.dev>