dt-bindings: clock: lan966x: Extend includes with clock gates

On lan966x it is allow to control the clock to some peripherals like
USB. So extend the include file with these clocks.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20211103085102.1656081-4-horatiu.vultur@microchip.com