ARM: dts: msm: Add extcon handle to QMP USB/DP PHY on sm8150

Add extcon reference to PM8150 PD to the QMP USB DP combo PHY
node. This allows the PHY to be notified whenever DP 2-lane
or 4-lane mode is used.

Change-Id: Ia300a03cd12c8991af1bfa6da99b5a3f0e34e3ff
Signed-off-by: Jack Pham <jackp@codeaurora.org>