dt-bindings: usb: atmel: Add Microchip LAN9662 compatible string

The USB device controller available in the Microchip LAN9662 SOC
is the same IP as the one present in the SAMA5D3 SOC.

Add the LAN9662 compatible string and set the SAMA5D3 compatible
string as a fallback for the LAN9662.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220704102845.168438-3-herve.codina@bootlin.com