Add usage for sysfs hw_pattern entry for leds-st1202

Signed-off-by: Vicentiu Galanopulo <vicentiu.galanopulo@remote-tech.co.uk>
Link: https://lore.kernel.org/r/20241218182001.41476-2-vicentiu.galanopulo@remote-tech.co.uk


Signed-off-by: Lee Jones <lee@kernel.org>