hw/arm/imx8mp-evk: Remove unimplemented cpu-idle-states properties from devicetree

The cpu-idle-states property causes a hard boot hang. Rather than documenting
the workaround, perform the removal from the devicetree automatically.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Bernhard Beschow <shentey@gmail.com>
[Bernhard: split patch, update documentation, adapt commit message]
Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Message-ID: <20250405214900.7114-3-shentey@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

docs/system/arm/imx8mp-evk.rst

@@ -35,7 +35,7 @@ Direct Linux Kernel Boot
 
 Probably the easiest way to get started with a whole Linux system on the machine
 is to generate an image with Buildroot. Version 2024.11.1 is tested at the time
-of writing and involves three steps. First run the following commands in the
+of writing and involves two steps. First run the following commands in the
 toplevel directory of the Buildroot source tree:
 
 .. code-block:: bash
@@ -50,14 +50,6 @@ it and resize the SD card image to a power of two:
 
   $ qemu-img resize sdcard.img 256M
 
-Finally, the device tree needs to be patched with the following commands which
-will remove the ``cpu-idle-states`` properties from CPU nodes:
-
-.. code-block:: bash
-
-  $ dtc imx8mp-evk.dtb | sed '/cpu-idle-states/d' > imx8mp-evk-patched.dts
-  $ dtc imx8mp-evk-patched.dts -o imx8mp-evk-patched.dtb
-
 Now that everything is prepared the machine can be started as follows:
 
 .. code-block:: bash
@@ -65,6 +57,6 @@ Now that everything is prepared the machine can be started as follows:
   $ qemu-system-aarch64 -M imx8mp-evk -smp 4 -m 3G \
       -display none -serial null -serial stdio \
       -kernel Image \
-      -dtb imx8mp-evk-patched.dtb \
+      -dtb imx8mp-evk.dtb \
       -append "root=/dev/mmcblk2p2" \
       -drive file=sdcard.img,if=sd,bus=2,format=raw,id=mmcblk2