doc: board: Convert i.MXRT1020 EVK 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/imxrt1020-evk.rst b/doc/board/freescale/imxrt1020-evk.rst
new file mode 100644
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+.. SPDX-License-Identifier: GPL-2.0+
+
+imxrt1020-evk
+=============
+
+How to use U-Boot on NXP i.MXRT1020 EVK
+---------------------------------------
+
+- Build U-Boot for i.MXRT1020 EVK:
+
+.. code-block:: bash
+
+   $ make mrproper
+   $ make imxrt1020-evk_defconfig
+   $ make
+
+This will generate the SPL image called SPL and the u-boot.img.
+
+- Flash the SPL image into the micro SD card:
+
+.. code-block:: bash
+
+   $sudo dd if=SPL of=/dev/sdX bs=1k seek=1 conv=notrunc; sync
+
+- Flash the u-boot.img image into the micro SD card:
+
+.. code-block:: bash
+
+   $sudo dd if=u-boot.img of=/dev/sdX bs=1k seek=128 conv=notrunc; sync
+
+- Jumper settings::
+
+   SW8: 0 1 1 0
+
+where 0 means bottom position and 1 means top position (from the
+switch label numbers reference).
+
+- Connect the USB cable between the EVK and the PC for the console.
+  The USB console connector is the one close the ethernet connector
+
+- Insert the micro SD card in the board, power it up and U-Boot messages should come up.