arm64: dts: fvp/juno: Fix bus node names

arm64: dts: fvp/juno: Fix bus node names

Most Arm Ltd. boards are employing a layered bus structure, to map
the hardware design (SoC, motherboard, IOFPGA) and structure the DTs.

The "simple-bus" nodes only allow a limited set of node names. Switch
to use *-bus to be binding compliant.

This relies on a pending dt-schema.git fix for now:
https://github.com/devicetree-org/dt-schema/pull/38

Link: https://lore.kernel.org/r/20200513103016.130417-16-andre.przywara@arm.com
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>