ARM: dts: msm: Add proxy init client for MM config slaves for sm8150

Due to the GDSCs now voting for slave config bandwidth, they can
potentially disconnect the multimedia configuration slaves from
CNOC preventing multimedia clock drivers from accessing their
clock controller register space. Keep a proxy vote to these
config slaves so that disconnect does not happen during probe.

Change-Id: I156f33aa7b809360aae6022f92d6ec071bcaf96a
Signed-off-by: David Dai <daidavid1@codeaurora.org>