leds: leds-pwm: Fix checkpatch warning

Fixes the following checkpatch warning:
WARNING: please, no space before tabs
	FILE: leds/leds-pwm.c:29:
		^Iunsigned int ^I^Iactive_low;$
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Bryan Wu <cooloney@gmail.com>