ARM: dts: r7s72100: stop grouping clocks under a "clocks" subnode

The current practice is to not group clocks under a "clocks" subnode,
but just put them together with the other on-SoC devices.

As per updates for R-Car Gen2 SoCs by Geert Uytterhoeven.

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