boards: imx943_evk: a55: update document about dcache

Update board document to remove dcache off command under U-Boot as
CONFIG_ARM64_BOOT_DISABLE_DCACHE has been enabled.

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

Author: JiafeiPan

boards/nxp/imx943_evk/doc/index.rst

@@ -83,13 +83,9 @@ Setup
 
 The default runner for the board is JLink, connect the EVK board's JTAG connector to
 the host computer using a J-Link debugger, power up the board and stop the board at
-U-Boot command line, execute the following U-boot command to disable D-Cache:
+U-Boot command line.
 
-.. code-block:: console
-
-    dcache off
-
-then use "west flash" or "west debug" command to load the zephyr.bin
+Then use "west flash" or "west debug" command to load the zephyr.bin
 image from the host computer and start the Zephyr application on A55 core0.
 
 Flash and Run
@@ -168,7 +164,7 @@ Use the following command to boot Zephyr on the core0:
 
 .. code-block:: console
 
-    dcache off; icache flush; go 0xd0000000;
+    dcache flush; icache flush; go 0xd0000000;
 
 Then the following log could be found on UART1 console: