platform/x86: asus-wmi: Only notify kbd LED hw_change by fn-key pressed

Since commit dbb3d78f ("platform/x86: asus-wmi: Call led hw_changed
API on kbd brightness change"), asus-wmi directly changes the keyboard
LED brightness when the keyboard brightness keys are pressed,
raising the appropriate notification.

However, this notification was unintentionally also being raised during
boot and resume from suspend. This was resulting in userspace showing
the keyboard LED OSD on resume for no good reason.

Move the keyboard LED brightness changed notification
from kbd_led_update to the new kbd_led_set_by_kbd function which is only
called from the keyboard brightness function keys codepath.

Signed-off-by: Jian-Hong Pan <jian-hong@endlessm.com>
Signed-off-by: Daniel Drake <drake@endlessm.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>