leds: leds-qpnp: Set WLED string current sinks

Set correct current sink when 1, 2 or 3 strings are in use.
Also, when using debug dumps, print all relevant registers.

Change-Id: Ib9ae9a959c3fcee0dcbb7b2882434cc6bcd126a3
Signed-off-by: Amy Maloche <amaloche@codeaurora.org>