leds: qpnp-wled: Disable the current sink conditionally

Disable the current sinks only if there is any change in the
configuration. Do not disable otherwise. This can avoid the
unnecessary flicker seen on the display during the bootup.

Change-Id: I2bcf6b542eec7c55f957cc62e98d85da9e7f6b40
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>