leds: led-class: Add Device Tree support to led_get()

leds: led-class: Add Device Tree support to led_get()

Add 'name' argument to of_led_get() such that it can lookup LEDs in
devicetree by either name or index.

And use this modified function to add devicetree support to the generic
(non devicetree specific) [devm_]led_get() function.

This uses the standard devicetree pattern of adding a -names string array
to map names to the indexes for an array of resources.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Hans de Goede <hansg@kernel.org>
Signed-off-by: Aleksandrs Vinarskis <alex@vinarskis.com>
Link: https://lore.kernel.org/r/20250910-leds-v5-3-bb90a0f897d5@vinarskis.com
Signed-off-by: Lee Jones <lee@kernel.org>