s390: kprobes: Use generic kretprobe trampoline handler

Use the generic kretprobe trampoline handler. Don't use
framepointer verification.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/159870612453.1229682.15950927742606892302.stgit@devnote2