arm64: dts: renesas: r8a77995: move nodes which have no reg property out of bus

Move pmu_a53 and timer nodes from soc node to root node.  The nodes that
have been moved do not have any register properties and thus shouldn't be
placed on the bus.

This problem is flagged by the compiler as follows:
$ make W=1
...
arch/arm64/boot/dts/renesas/r8a77995-draak.dtb: Warning (simple_bus_reg): Node /soc/timer missing or empty reg/ranges property
arch/arm64/boot/dts/renesas/r8a77995-draak.dtb: Warning (simple_bus_reg): Node /soc/pmu_a53 missing or empty reg/ranges property

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>