dt-bindings: usb: xhci: Add Broadcom STB v2 compatible device

For some reason the "brcm,xhci-brcm-v2" compatible string has been missing
in the original bindings file. Add it to the Generic xHCI Controllers DT
schema since the controller driver expects it to be supported.

Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201210090944.16283-9-Sergey.Semin@baikalelectronics.ru


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>