1. Remove the gpio 26 config in board-flo-pmic.c
since this gpio is already config as PWM function in LK.
2. Add pwm_init function implementation.
3. Config backlight level in pm8xxx_led_probe(), and remove the
pwm_request() part in panel probe function.
Change-Id: I3ce71a9c792ce155bebabd80a24a8ff8fc361ae9
Signed-off-by: yetta_wu <yetta_wu@asus.com>