ARM: dts: msm: add extcon pdphy to sde_dp for sm8150

To listen to PDPHY notifications for USB cable connect/disconnect,
add pdphy extcon handler to SDE DP device tree node.

CRs-Fixed: 2338665
Change-Id: Ib91840a03cbf8f4b84427c98ab7139de87b1ef31
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>