ARM: dts: imx6q-cm-fx6: add sdio wifi/bt nodes

The cm-fx6 module has an on-board AW-NH387 WiFi/BT module which is
based on Marvell's SD8787 chip and is connected to the usdhc1
controller.

Unfortunately, the chip gets unresponsive if the Bluetooth AMP
(Alternate Mac/Phy) function gets probed but the loaded firmware
doesn't support it. For instance, this is the case for the most
recent firmware in linux-firmware (Version 14.66.35.p52).

Thus, just add the required nodes but leave the usdhc1 node disabled
explicitly. Users who disabled the Bluetooth (AMP) support of their
OS can then conveniently enable WiFi (or even plain Bluetooth) support
with a simple device tree overlay/bootloader configuration.

Signed-off-by: Christopher Spinrath <christopher.spinrath@rwth-aachen.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>