samples: shell_module: add imx93 board support

Add kernel reboot support, so can use shell to verify reboot function.
uart:~$ kernel reboot cold
Known issue is imx93 currently can only support cold reboot and doen't
support warm reboot.

Updated board document.

Signed-off-by: Jiafei Pan <Jiafei.Pan@nxp.com>

Author: JiafeiPan

boards/nxp/imx93_evk/doc/index.rst

@@ -175,6 +175,26 @@ display the following console output:
     thread_a: Hello World from cpu 0 on imx93_evk!
     thread_b: Hello World from cpu 0 on imx93_evk!
 
+System Reboot (A55)
+===================
+
+Currently i.MX93 only support cold reboot and doesn't support warm reboot.
+Use this configuratiuon to verify cold reboot with :zephyr:code-sample:`shell-module`
+sample:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/subsys/shell/shell_module
+   :host-os: unix
+   :board: imx93_evk/mimx9352/a55
+   :goals: build
+
+This will build an image with the shell sample app, boot it and execute
+kernel reboot command in shell command line:
+
+.. code-block:: console
+
+    uart:~$ kernel reboot cold
+
 Programming and Debugging (M33)
 *******************************
 

samples/subsys/shell/shell_module/boards/imx93_evk_mimx9352_a55.conf

@@ -0,0 +1,3 @@
+CONFIG_REBOOT=y
+CONFIG_PM_CPU_OPS=y
+CONFIG_PM_CPU_OPS_PSCI=y