leds: leds-bd2802: add CONFIG_PM_SLEEP to suspend/resume functions

Add CONFIG_PM_SLEEP to suspend/resume functions to fix the following
build warning when CONFIG_PM_SLEEP is not selected. This is because
sleep PM callbacks defined by SIMPLE_DEV_PM_OPS are only used when
the CONFIG_PM_SLEEP is enabled.

drivers/leds/leds-bd2802.c:766:12: warning: 'bd2802_suspend' defined but not used [-Wunused-function]
drivers/leds/leds-bd2802.c:776:12: warning: 'bd2802_resume' defined but not used [-Wunused-function]

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>