leds: leds-qpnp: Enable watchdog timer for flash torch mode

Flash LED raises module temperature when turned on. Current
implementation disables timers in torch mode and this creates
potential risk of module damage due to raised temperature.
When flash LED is used as torch, watchdog timer should be enabled
to allow hardware to turn LEDs off according to predefined
duration.

Change-Id: I3768a04abd59c12f6bd1c355a5e194b1fa5b2bc4
Signed-off-by: Chun Zhang <chunz@codeaurora.org>