nvme-cli: cleanup comments for telemetry log structure

nvme-cli: cleanup comments for telemetry log structure

This removes three comments for struct nvme_telemetry_log_page_hdr.

- The comment on top of the definision doesn't describe more than the
  struct name itself.

- The rsvd1 field has already been verified.

- The structures with trailing zero size array are commonly used in
  nvme-cli, so we don't need special comment for telemetry_dataarea[0].

Cc: Keith Busch <keith.busch@intel.com>
Cc: Jens Axboe <axboe@fb.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Kenneth Heitke <kenneth.heitke@intel.com>
Suggested-by: Kenneth Heitke <kenneth.heitke@intel.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>