ARM: dts: msm: add DT property for sync write delay for WLED

Add DT property for sync write delay for WLED module, which is needed
between two consecutive sync register writes, for MSM8937 MTP
and CDP that uses PMI8950 and PMI8937.

Change-Id: Ib7078948f286f7b949f1cbbd0b42be5b89df2c6a
Signed-off-by: Shantanu Jain <shjain@codeaurora.org>