leds: fix aat1290 build errors

Fix build errors when LEDS_AAT1290=y and V4L2_FLASH_LED_CLASS=m
by restricting LEDS_AAT1290 to =m if V4L2_FLASH_LED_CLASS=m.

drivers/built-in.o: In function `aat1290_led_remove':
leds-aat1290.c:(.text+0xe5d77): undefined reference to `v4l2_flash_release'
drivers/built-in.o: In function `aat1290_led_probe':
leds-aat1290.c:(.text+0xe6494): undefined reference to `v4l2_flash_init'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Richard Purdie <rpurdie@rpsys.net>
Acked-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>