leds: qti-flash: Allow dynamic symmetry current redistribution

Currently, when symmetry is enabled, current redistribution occurs only
when a switch is turned on after being disabled initially. Enable
current redistribution to occur on the fly as long as a switch is
enabled. This applies to both torch and flash devices.

Illustrative example:

user0	user3	Torch0	Torch3	Comment
500	0	250	250	(average of user set values)
150	0	75	75	(150 + 0 / 2)
150	100	125	125	(150 + 100 / 2).

Change-Id: I5f832e4fa669a9662d45592c5c3a512df07f7255
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>