bpf, x64: Remove tail call detection

As 'prog->aux->tail_call_reachable' is correct for tail call present,
it's unnecessary to detect tail call in x86 jit.

Therefore, let's remove it.

Signed-off-by: Leon Hwang <hffilwlqm@gmail.com>
Link: https://lore.kernel.org/r/20240610124224.34673-3-hffilwlqm@gmail.com


Signed-off-by: Alexei Starovoitov <ast@kernel.org>