ARM: dts: msm: Delete extcon property on sdxprairie RUMI

PM8150B is not available on sdxprairie RUMI. This would result
into no USB cable connect/disconnect detection functionality.
Hence delete extcon property to avoid QPNP PDPHY driver probe
and SPMI write related error from it.

Change-Id: I4325965731a977cc8d57540491172c10b34813f0
Signed-off-by: Mayank Rana <mrana@codeaurora.org>