ARM: dts: r8a77470: Add USB2.0 Host (EHCI/OHCI) device

Define the r8a77470 generic part of the USB2.0 Host Controller device
nodes (ehci[01]/ohci[01]).

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