leds: ns2: Slightly simplify a memory allocation

Use devm_kcalloc() instead of devm_kzalloc()+array_size().

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/560b8f140c19a7da40f5e9540c3ef312969b0dc4.1690057595.git.christophe.jaillet@wanadoo.fr


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