dt-bindings: usb: snps,dwc3: correct i.MX8MQ support

The previous i.MX8MQ support breaks rockchip,dwc3 support,
so use select to restrict i.MX8MQ support and avoid break others.

Fixes: 3754c41c7686 ("dt-bindings: usb: snps,dwc3: support i.MX8MQ")
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230323035531.3808192-1-peng.fan@oss.nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>