leds: leds-qpnp: Enable flash torch mode on single LED PMIC

Flash LED torch mode is not supported from hardware perspective
on PMIC with single flash LED module. Enabling torch mode on such
PMIC chips requires detection of PMIC peripheral subtype and
use flash mode with a lower current to implement torch.

Change-Id: I77228068c2c0ec4a0ed5614f4a991a3bce5db013
Signed-off-by: Chun Zhang <chunz@codeaurora.org>