ARM: dts: r8a7745: initial SoC device tree

The  initial R8A7745 SoC device tree including CPU0, GIC, timer, SYSC, RST,
CPG, and the required clock descriptions.

Based on the original (and large) patch by Dmitry Shifrin
<dmitry.shifrin@cogentembedded.com>.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>