ARM: dts: r8a77470: Add HSUSB device nodes

Define the r8a77470 generic part of the HSUSB0/1 device nodes.

Currently the renesas_usbhs driver doesn't handle multiple phys and we
don't have a proper hardware to validate such driver changes.

So for hsusb1 it is assumed that usbphy0 will be enabled by either
channel0 host or device.

In future, if any boards support hsusb1, we will need to add multiple phy
support in the renesas_usbhs driver and override the board dts to enable
the same.

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