leds: Make leds_class a static const structure

leds: Make leds_class a static const structure

Now that the driver core allows for struct class to be in read-only
memory, move the leds_class structure to be declared at build time
placing it into read-only memory, instead of having to be dynamically
allocated at boot time.

Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com>
Link: https://lore.kernel.org/r/20230810174905.7997-1-ivan.orlov0322@gmail.com
Signed-off-by: Lee Jones <lee@kernel.org>