ARM: dts: msm: Add modem qrtr node for sm8150-sdxprairie

For certain usecases the internal modem will be brought out of reset.
Set the net id to 2 so the packets coming from the internal modem
are not forwarded to other Q6 or SDX.

Change-Id: I439f42128bced10001197182fd58a695c782a4b9
Signed-off-by: Chris Lew <clew@codeaurora.org>