ARM: dts: r8a7794: Fix W=1 dtc warnings

Warning (unit_address_vs_reg): Node /cache-controller@1 has a unit name, but no reg property

Move the cache-controller node under the cpus node, and make its unit
name and reg property match the MPIDR value.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>