arm64: dts: renesas: r8a774a1: Add I2C and IIC-DVFS support

Add the I2C[0-6] and IIC Bus Interface for DVFS (IIC for DVFS)
devices nodes to the r8a774a1 device tree.

Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>