MLK-21830-2 DTS: imx8qm: Add DTS and binding header files

MLK-21830-2 DTS: imx8qm: Add DTS and binding header files

Copy the imx8qm DTS files from imx_4.14.y kernel (rel_imx_4.14.98_2.0.0_ga_rc1)

Add extra support used in u-boot:
1. Add mbox-cells used for mailbox
2. Add alias for FSPI nodes
3. Add the usb alias for OTG and USB3.
4. Add "u-boot,dm-pre-reloc" to thermal node to DTSi
5. Add "simple-bus" compatible strings to imx8qm-pm node.

Signed-off-by: Ye Li <ye.li@nxp.com>
(cherry picked from commit f9e19d1f64424b11c8438b3d09ce336a9579f99f)
(cherry picked from commit 7a60e2803535ca1cffed18c3b288004b0decefa0)