It is helpful to trace the flushing completions of isochronous context when
the core function is requested them by both in-kernel unit drivers and
userspace applications.

This commit adds some tracepoints events for the aim.

Link: https://lore.kernel.org/r/20240623220859.851685-6-o-takashi@sakamocchi.jpSigned-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>