Revert "dt-bindings: usb: cdns,usb3: document USBSSP controller support"

This reverts commit fb14e7f7cbb4abbcde5576282d91352deaff2887.

There were some build issues as reported by Arnd, so revert this for
now.

Cc: Peter Chen <peter.chen@cixtech.com>
Cc: Pawel Laszczak <pawell@cadence.com>
Reported-by: Arnd Bergmann <arnd@kernel.org>
Link: https://lore.kernel.org/r/ac+LEWMCQpLSnfoD@nchen-desktop
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>