leds: ipaq-micro: fix sparse non static symbol warning

Fixes the following sparse warnings:

drivers/leds/leds-ipaq-micro.c:130:24: warning:
 symbol 'micro_leds_device_driver' was not declared. Should it be static?

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Bryan Wu <cooloney@gmail.com>