arm64: dts: imx8mq-evk: Enable the QuadSPI controller

Enable the Freescale/NXP QuadSPI controller with a proper pinctrl set on
the i.MX8MQ EVK board.

Signed-off-by: Carlo Caione <ccaione@baylibre.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>