led: leds-qpnp: Enable individual flash LED control

Existing implementation turns on and off both flash LEDs simultaneously
due to earlier hardware bug. With hardware bug removed, enabling flash
LED individual control allows user to turn on or off one flash LED at a
time.

CRs-Fixed: 498526
Change-Id: I95448e1886dc2aba2da7bb4845c1b5993b3fe0da
Signed-off-by: Chun Zhang <chunz@codeaurora.org>