ARM: dts: msm: add DT property for sync write delay for WLED PMI8950/37

Add DT property for sync write delay for WLED module, which is needed
between two consecutive sync register writes.

CRs-Fixed: 1004676
Change-Id: If7869ecdbdb2c9ca67742bcf9e8ee4ecbaf0b0be
Signed-off-by: Abinaya P <abinayap@codeaurora.org>