ARM: dts: bcm2711: Add reset controller to xHCI node

The chip is hardwired to the board's PCIe bus and needs to be properly
setup trough a firmware routine after a PCI fundamental reset. Pass the
reset controller phandle that takes care of triggering the
initialization to the relevant PCI device.

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Link: https://lore.kernel.org/r/20200629161845.6021-5-nsaenzjulienne@suse.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>