ARM: dts: msm: Move extcon entry into overlay for sdm670

Move extcon entry to board specific device tree overlay.
Add vbus and vconn entry for pdphy. It will get overridden
in sdm670-pmic-overlay.dtsi where all the device nodes has
been moved.

Change-Id: I1e0639412612ea65fe0fb92552427e32d4c73357
Signed-off-by: Pratham Pratap <prathampratap@codeaurora.org>