Document newly added "count_clock" sysfs entry for the Mellanox
BlueField PMC driver.

Signed-off-by: Shravan Kumar Ramani <shravankr@nvidia.com>
Reviewed-by: David Thompson <davthompson@nvidia.com>
Link: https://lore.kernel.org/r/367301238efff01fc200c67bca461c0424baf95d.1736413033.git.shravankr@nvidia.com


[ij: corrected KernelVersion & Date]
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>