x86,kprobes: Fix optprobe trampoline to generate complete pt_regs

x86,kprobes: Fix optprobe trampoline to generate complete pt_regs

Currently the optprobe trampoline template code ganerate an
almost complete pt_regs on-stack, everything except regs->ss.
The 'regs->ss' points to the top of stack, which is not a
valid segment decriptor.

As same as the rethook does, complete the job by also pushing ss.

Suggested-by: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>
Link: https://lore.kernel.org/bpf/164826166027.2455864.14759128090648961900.stgit@devnote2