ARM: dts: msm: specify delay between two writes to SYNC for 8952

For 8952 WLED, add an optional DT property - qcom,cons-sync-
write-delay-us to specify the delay duration between two
consecutive writes to SYNC register of WLED SINK block.
Also, increase the full scale current value of WLED to 30mA
as per the recommendations from PMIC Systems Team to achieve
maximum brightness of WLED.

Change-Id: I51f5146f3f22a45e9500095124c4fe0b638ae36c
Signed-off-by: Abinaya P <abinayap@codeaurora.org>