Convert CONFIG_CMD_ENV_FLAGS to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_ENV_FLAGS

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/README b/README
index a785dbf..99c10c2 100644
--- a/README
+++ b/README
@@ -833,7 +833,6 @@
 		CONFIG_CMD_ECHO		  echo arguments
 		CONFIG_CMD_EDITENV	  edit env variable
 		CONFIG_CMD_ELF		* bootelf, bootvx
-		CONFIG_CMD_ENV_FLAGS	* display details about env flags
 		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
 		CONFIG_CMD_EXPORTENV	* export the environment
 		CONFIG_CMD_EXT2		* ext2 command support
diff --git a/cmd/Kconfig b/cmd/Kconfig
index 3ac8764..ab09a9f 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -322,6 +322,14 @@
 	  For example changing "baudrate" adjust the serial baud rate. This
 	  command lists the currently defined callbacks.
 
+config CMD_ENV_FLAGS
+	bool "env flags -print variables that have non-default flags"
+	help
+	  Some environment variables have special flags that control their
+	  behaviour. For example, serial# can only be written once and cannot
+	  be deleted. This command shows the variables that have special
+	  flags.
+
 endmenu
 
 menu "Memory commands"
diff --git a/configs/ids8313_defconfig b/configs/ids8313_defconfig
index 165e2eb..2accd31 100644
--- a/configs/ids8313_defconfig
+++ b/configs/ids8313_defconfig
@@ -13,6 +13,7 @@
 CONFIG_AUTOBOOT_KEYED=y
 CONFIG_AUTOBOOT_PROMPT="Enter password - autoboot in %d seconds...\n"
 CONFIG_AUTOBOOT_DELAY_STR="ids"
+CONFIG_CMD_ENV_FLAGS=y
 CONFIG_CMD_SPI=y
 CONFIG_CMD_I2C=y
 # CONFIG_CMD_SETEXPR is not set
diff --git a/configs/sandbox_defconfig b/configs/sandbox_defconfig
index 410277a..9e46fa6 100644
--- a/configs/sandbox_defconfig
+++ b/configs/sandbox_defconfig
@@ -23,6 +23,7 @@
 CONFIG_CMD_ASKENV=y
 CONFIG_CMD_GREPENV=y
 CONFIG_CMD_ENV_CALLBACK=y
+CONFIG_CMD_ENV_FLAGS=y
 CONFIG_CMD_MD5SUM=y
 CONFIG_LOOPW=y
 CONFIG_CMD_MEMTEST=y
diff --git a/configs/sandbox_noblk_defconfig b/configs/sandbox_noblk_defconfig
index 090e057..4bf1f4b 100644
--- a/configs/sandbox_noblk_defconfig
+++ b/configs/sandbox_noblk_defconfig
@@ -23,6 +23,7 @@
 CONFIG_CMD_ASKENV=y
 CONFIG_CMD_GREPENV=y
 CONFIG_CMD_ENV_CALLBACK=y
+CONFIG_CMD_ENV_FLAGS=y
 CONFIG_CMD_MD5SUM=y
 CONFIG_LOOPW=y
 CONFIG_CMD_MEMTEST=y
diff --git a/configs/sandbox_spl_defconfig b/configs/sandbox_spl_defconfig
index b623e29..cbe4185 100644
--- a/configs/sandbox_spl_defconfig
+++ b/configs/sandbox_spl_defconfig
@@ -31,6 +31,7 @@
 CONFIG_CMD_ASKENV=y
 CONFIG_CMD_GREPENV=y
 CONFIG_CMD_ENV_CALLBACK=y
+CONFIG_CMD_ENV_FLAGS=y
 CONFIG_CMD_MD5SUM=y
 CONFIG_LOOPW=y
 CONFIG_CMD_MEMTEST=y
diff --git a/include/configs/ids8313.h b/include/configs/ids8313.h
index 17944a9..69e2b9e 100644
--- a/include/configs/ids8313.h
+++ b/include/configs/ids8313.h
@@ -444,7 +444,6 @@
 #define CONFIG_UBOOTPATH		"ids8313/u-boot.bin"
 #define CONFIG_FDTFILE			"ids8313/ids8313.dtb"
 #define CONFIG_LOADADDR		0x400000
-#define CONFIG_CMD_ENV_FLAGS
 #define CONFIG_ENV_FLAGS_LIST_STATIC "ethaddr:mo,eth1addr:mo"
 
 /* Initial Memory map for Linux*/
diff --git a/include/configs/sandbox.h b/include/configs/sandbox.h
index 9aa18d4..9d69fa2 100644
--- a/include/configs/sandbox.h
+++ b/include/configs/sandbox.h
@@ -107,8 +107,6 @@
 
 #define CONFIG_CMD_SANDBOX
 
-#define CONFIG_CMD_ENV_FLAGS
-
 #define CONFIG_BOOTARGS ""
 
 #ifndef SANDBOX_NO_SDL
diff --git a/scripts/config_whitelist.txt b/scripts/config_whitelist.txt
index 0cece7d..e51ddb8 100644
--- a/scripts/config_whitelist.txt
+++ b/scripts/config_whitelist.txt
@@ -383,7 +383,6 @@
 CONFIG_CMDLINE_EDITING
 CONFIG_CMDLINE_PS_SUPPORT
 CONFIG_CMDLINE_TAG
-CONFIG_CMD_ENV_FLAGS
 CONFIG_CMD_ERRATA
 CONFIG_CMD_ESBC_VALIDATE
 CONFIG_CMD_ETHSW