leds: ns2: alloc simple array instead of struct ns2_led_priv

Since .remove method is not needed now that we use devres, there is no
need to remember the number of LEDs in struct ns2_led_priv. Alloc simple
array of ns2_led_data structs.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Cc: Simon Guinot <simon.guinot@sequanux.org>
Cc: Simon Guinot <sguinot@lacie.com>
Cc: Vincent Donnefort <vdonnefort@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Pavel Machek <pavel@ucw.cz>