arm64: dts: fvp: Move fixed clocks out of bus node
The devicetree compiler complains when DT nodes without a reg property
live inside a (simple) bus node:
Warning (simple_bus_reg): Node /bus@
8000000/v2m_refclk32khz
missing or empty reg/ranges property
Move the fixed clocks to the root node, since they do not depend on any
busses.
Link: https://lore.kernel.org/r/20200513103016.130417-6-andre.przywara@arm.com
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>