ARM: dts: msm: Use correct VDCCX voting for WCNSS for msm8939

For VDDCX, WCNSS pltfrom driver has to vote for S2 regulator.
Hence vote for S2 regulator for VDDCX.

Change-Id: I1f4b7e3916a134875ca81082cc8416d0bbbe93ff
CRs-Fixed: 674425
Signed-off-by: Hardik Kantilal Patel <hkpatel@codeaurora.org>