bpf: Use ftrace_get_symaddr() for kprobe_multi probes

bpf: Use ftrace_get_symaddr() for kprobe_multi probes

Add ftrace_get_entry_ip() which is only for ftrace based probes, and use
it for kprobe multi probes because they are based on fprobe which uses
ftrace instead of kprobes.

Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Florent Revest <revest@chromium.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: bpf <bpf@vger.kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Alan Maguire <alan.maguire@oracle.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/173566081414.878879.10631096557346094362.stgit@devnote2
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>