dt-bindings: net: mscc-miim: Add resets property

Add the (optional) resets property.
The mscc-miim device is impacted by the switch reset especially when the
mscc-miim device is used as part of the LAN966x PCI device.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>