dt-bindings: usb: generic-ehci: Add HPE GXP ehci binding

Add hpe,gxp-ehci to the generic-ehci list. This is to
enable the device tree.

Signed-off-by: Nick Hawkins <nick.hawkins@hpe.com>
Link: https://lore.kernel.org/r/20220421192132.109954-9-nick.hawkins@hpe.com


Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>