leds: aw2016: update breath sysfs node name

Update the blink sysfs node name to "breath"
to make sure the userspace code can access it
correctly. Meanwhile, replace msleep() with
usleep_range() for better sleeping delay precision,
and update the device sysfs node permission to 0644.

Change-Id: I0957087747fcf01f5a036f25c44ce83787b071a9
Signed-off-by: Hui Liu <huliu@codeaurora.org>