ARM: dts: msm: Enable auto-calibration for WLED on PM660/PMI8998

The auto-calibration logic dynamically detects the valid
strings (sinks) configured for that target.

CRs-Fixed: 2011194
Change-Id: Id6c9c148d1662baca33d3cde343aafff40b27c22
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>