arm64: dts: Add USB DT nodes for Stingray SoC

Add DT nodes for
  - Two xHCI host controllers
  - Two BDC Broadcom USB device controller
  - Five USB PHY controllers

[xHCI0]      [BDC0]            [xHCI1]            [BDC1]
   |           |                  |                 |
  ---------------               -----------------------
   |           |                 |         |         |
[SS-PHY0]   [HS-PHY0]        [SS-PHY1] [HS-PHY2] [HS-PHY1]

[SS-PHY0/HS-PHY0] and [SS-PHY1/HS-PHY1] are combo PHYs has one SS and
one HS PHYs. [HS-PHY2] is a single HS PHY.

xHCI use SS-PHY to detect SS devices and HS-PHY to detect HS/FS/LS
devices. BDC use SS-PHY in SS mode and HS-PHY in HS mode.

xHCI0 port1 is SS-PHY0, port2 is HS-PHY0.
xHCI1 port1 is SS-PHY1, port2 is HS-PHY2 and port3 is HS-PHY1.

Signed-off-by: Srinath Mannam <srinath.mannam@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>