leds-lm3530: remove LM3530_ALS_ZONE_REG code

LM3530_ALS_ZONE_REG is read-only register.
Writing this register is not necessary.

Signed-off-by: Milo(Woogyom) Kim <milo.kim@ti.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>