docs: trace: Add HiSilicon PTT device driver documentation

docs: trace: Add HiSilicon PTT device driver documentation

Document the introduction and usage of HiSilicon PTT device driver as well
as the sysfs attributes description provided by the driver.

Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
[Fixed month and kernel version]
Link: https://lore.kernel.org/r/20220816114414.4092-5-yangyicong@huawei.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>