ARM: dts: msm: add LOWSVS support on sdm670

Update IPA node to have LOWSVS entry
to vote for LOWSVS power mode.

Change-Id: I9b2b1158fc4de4319860f424ac2dd5e734a22841
Acked-by: Ashok Vuyyuru <avuyyuru@qti.qualcomm.com>
Signed-off-by: Mohammed Javid <mjavid@codeaurora.org>