dt-bindings: net: micrel-ksz90x1.txt: Update for lan8841

The lan8841 has the same bindings as ksz9131, so just reuse the entire
section of ksz9131.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>