doc: imx8mp-evk: update after using binman

update doc after using binman to pack images

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/doc/board/freescale/imx8mp_evk.rst b/doc/board/freescale/imx8mp_evk.rst
index 796a761..609a29f 100644
--- a/doc/board/freescale/imx8mp_evk.rst
+++ b/doc/board/freescale/imx8mp_evk.rst
@@ -40,18 +40,19 @@
    $ export CROSS_COMPILE=aarch64-poky-linux-
    $ make O=build imx8mp_evk_defconfig
    $ cp ../imx-atf/build/imx8mp/release/bl31.bin ./build/bl31.bin
-   $ cp ../firmware-imx-8.10/firmware/ddr/synopsys/lpddr4_pmu_train_1d_dmem_202006.bin ./build/lpddr4_pmu_train_1d_dmem.bin
-   $ cp ../firmware-imx-8.10/firmware/ddr/synopsys/lpddr4_pmu_train_1d_imem_202006.bin ./build/lpddr4_pmu_train_1d_imem.bin
-   $ cp ../firmware-imx-8.10/firmware/ddr/synopsys/lpddr4_pmu_train_2d_dmem_202006.bin ./build/lpddr4_pmu_train_2d_dmem.bin
-   $ cp ../firmware-imx-8.10/firmware/ddr/synopsys/lpddr4_pmu_train_2d_imem_202006.bin ./build/lpddr4_pmu_train_2d_imem.bin
+   $ cp ../firmware-imx-8.10/firmware/ddr/synopsys/lpddr4_pmu_train_1d_dmem_202006.bin ./build/
+   $ cp ../firmware-imx-8.10/firmware/ddr/synopsys/lpddr4_pmu_train_1d_imem_202006.bin ./build/
+   $ cp ../firmware-imx-8.10/firmware/ddr/synopsys/lpddr4_pmu_train_2d_dmem_202006.bin ./build/
+   $ cp ../firmware-imx-8.10/firmware/ddr/synopsys/lpddr4_pmu_train_2d_imem_202006.bin ./build/
    $ export ATF_LOAD_ADDR=0x970000
-   $ make O=build flash.bin
+   $ make O=build
 
 Burn the flash.bin to the MicroSD card at offset 32KB:
 
 .. code-block:: bash
 
    $sudo dd if=build/flash.bin of=/dev/sd[x] bs=1K seek=32 conv=notrunc; sync
+   $sudo dd if=build/u-boot.itb of=/dev/sd[x] bs=1K seek=384 conv=notrunc; sync
 
 Boot
 ----