leds: led-qti-tri-led: Remove default blink on/off values

Remove the default blink on/off values to make the LEDs can only be
blinking after the delay_on/off parameters are set. Also set
LED_KEEP_TRIGGER flag to the LED devices so the trigger can be kept
when it's turned off.

Change-Id: Ie6210cc7fcdc388f953a3969b7ba90761cbcd07f
Signed-off-by: Fenglin Wu <fenglinw@codeaurora.org>