dt-bindings: hwmon: emc2305: Add fan-shutdown-percent property

dt-bindings: hwmon: emc2305: Add fan-shutdown-percent property

The EMC2305 fan controller supports multiple independent PWM fan
outputs. Some systems require fans to enter a defined safe state
during system shutdown or reboot handoff, until firmware or the next
boot stage reconfigures the controller.

Add an optional "fan-shutdown-percent" property to fan child nodes
allowing the PWM duty cycle applied during shutdown to be configured
per fan output.

Signed-off-by: Florin Leotescu <florin.leotescu@nxp.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20260429065955.2113012-3-florin.leotescu@oss.nxp.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>