leds: leds-qpnp-flash: change to dynamic LED trigger

Change to dynamic LED trigger, in order to update strobe
trigger register as per LED request events. This change
helps to trigger only requested LED and isolate
other LEDs.

Change-Id: I6f3bcefa02513ff653b1857760c3b32de02365a9
Signed-off-by: Jigarkumar Kishorkumar Zala <j_zala@codeaurora.org>