x86/kprobes: Use generic kretprobe trampoline handler

Use the generic kretprobe trampoline handler. Use regs->sp
for framepointer verification.

[ mingo: Minor edits. ]

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/159870601250.1229682.14598707734683575237.stgit@devnote2