u-boot-stm32mp-extlinux: Pass ro to kernel cmdline

Default configuration uses `rw`. We default now to read-only root
filesystems so we switch the argument accordingly.

Signed-off-by: Andrei Gherzan <andrei.gherzan@huawei.com>

meta-ohos-core/recipes-bsp/u-boot/u-boot-stm32mp-extlinux.bbappend

@@ -2,6 +2,8 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
+UBOOT_EXTLINUX_KERNEL_ARGS = "rootwait ro"
+
 inherit deploy
 
 do_deploy[sstate-outputdirs] = "${DEPLOY_DIR_IMAGE}/bootloader/extlinux"