Allow a minimal setup of the r8a7779 SoC using a flattened device tree.
In particular, configure the i2c and ethernet controllers using a
flattened device tree.

SCI serial controller and TMU clock source, whose drivers do not yet
support configuration using a flattened device tree, are still configured
using C code in order to allow booting of a board with this SoC.

The ethernet controller also requires a regulator which is a board property.
A sample snippet DT for the marzen board is as follows:

/dts-v1/;
/include/ "r8a7779.dtsi"

/ {
	fixedregulator3v3: fixedregulator@0 {
		compatible = "regulator-fixed";
		regulator-name = "fixed-3.3V";
		regulator-min-microvolt = <3300000>;
		regulator-max-microvolt = <3300000>;
		regulator-boot-on;
		regulator-always-on;
	};
};

&lan0 {
	vddvario-supply = <&fixedregulator3v3>;
	vdd33a-supply = <&fixedregulator3v3>;
};
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>