doc: board: Convert i.MX8QXP MEK README to reST

Convert plain text documentation to reStructuredText format and add
it to Sphinx TOC tree. No essential content change.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/doc/board/freescale/imx8qxp_mek.rst b/doc/board/freescale/imx8qxp_mek.rst
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+.. SPDX-License-Identifier: GPL-2.0+
+
+imx8qxp_mek
+===========
+
+U-Boot for the NXP i.MX8QXP EVK board
+
+Quick Start
+-----------
+
+- Build the ARM Trusted firmware binary
+- Get scfw_tcm.bin and ahab-container.img
+- Build U-Boot
+- Flash the binary into the SD card
+- Boot
+
+Get and Build the ARM Trusted firmware
+--------------------------------------
+
+.. code-block:: bash
+
+   $ git clone https://source.codeaurora.org/external/imx/imx-atf
+   $ cd imx-atf/
+   $ git checkout origin/imx_4.19.35_1.1.0 -b imx_4.19.35_1.1.0
+   $ make PLAT=imx8qx bl31
+
+Get scfw_tcm.bin and ahab-container.img
+---------------------------------------
+
+.. code-block:: bash
+
+   $ wget https://www.nxp.com/lgfiles/NMG/MAD/YOCTO/imx-sc-firmware-1.2.7.1.bin
+   $ chmod +x imx-sc-firmware-1.2.7.1.bin
+   $ ./imx-sc-firmware-1.2.7.1.bin
+   $ wget https://www.nxp.com/lgfiles/NMG/MAD/YOCTO/imx-seco-2.3.1.bin
+   $ chmod +x imx-seco-2.3.1.bin
+   $ ./imx-seco-2.3.1.bin
+
+Copy the following binaries to U-Boot folder:
+
+.. code-block:: bash
+
+  $ cp imx-atf/build/imx8qx/release/bl31.bin .
+  $ cp imx-seco-2.3.1/firmware/seco/mx8qx-ahab-container.img ./ahab-container.img
+  $ cp imx-sc-firmware-1.2.7.1/mx8qx-mek-scfw-tcm.bin	.
+
+Build U-Boot
+------------
+
+.. code-block:: bash
+
+  $ make imx8qxp_mek_defconfig
+  $ make flash.bin
+
+Flash the binary into the SD card
+---------------------------------
+
+Burn the flash.bin binary to SD card offset 32KB:
+
+.. code-block:: bash
+
+   $ sudo dd if=flash.bin of=/dev/sd[x] bs=1024 seek=32 conv=notrunc
+
+Boot
+----
+Set Boot switch SW2: 1100.