ARM: dts: msm: Add support for IPA clock voting by bus driver

Due to RPMH support at sdm845, IPA clock voting needs
to go through BCM. This means that IPA clock voting needs
to be done by msm-bus-scaling driver instead of Linux
clock driver.
Add dts entry to distinguish between the two modes.

Change-Id: I3190d700dbdd172230afc5f14d912afbaec37832
Signed-off-by: Ghanim Fodi <gfodi@codeaurora.org>