configs: Add support in Kconfig and convert for armada boards

Move the DEFAULT_ENV_IS_RW to Kconfig for easier configuration.
Hence, add the CONFIG_DEFAULT_ENV_IS_RW config to the defconfig files
to allow enabling them for armada boards.

Signed-off-by: Algapally Santosh Sagar <santoshsagar.algapally@amd.com>
Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu@amd.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Link: https://lore.kernel.org/r/20230921112043.3144726-2-venkatesh.abbarapu@amd.com
Signed-off-by: Michal Simek <michal.simek@amd.com>
diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 9f0f84c..8761a64 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -24,6 +24,12 @@
 	  in the SPL stage (most drivers) or for choosing a default baudrate
 	  in the absence of an environment setting (serial_mxc.c).
 
+config DEFAULT_ENV_IS_RW
+	bool "Make default environment as writable"
+	help
+	  Select this to enable to make default environment writable. This
+	  allows modifying the default environment.
+
 config REQUIRE_SERIAL_CONSOLE
 	bool "Require a serial port for console"
 	# Running without a serial console is not supported by the