Convert CONFIG_CMD_STRINGS to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_STRINGS

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

cmd/Kconfig

@@ -492,6 +492,14 @@ config SHA1SUM_VERIFY
 	help
 	  Add -v option to verify data against a SHA1 checksum.
 
+config CMD_STRINGS
+	bool "strings - display strings in memory"
+	help
+	  This works similarly to the Unix 'strings' command except that it
+	  works with a memory range. String of printable characters found
+	  within the range are displayed. The minimum number of characters
+	  for a sequence to be considered a string can be provided.
+
 endmenu
 
 menu "Compression commands"

include/configs/vct.h

@@ -239,7 +239,6 @@ int vct_gpio_get(int pin);
  * (NOR/OneNAND) usage and Linux kernel booting.
  */
 #if defined(CONFIG_VCT_SMALL_IMAGE)
-#undef CONFIG_CMD_STRINGS
 #undef CONFIG_CMD_TERMINAL
 
 #undef CONFIG_SMC911X

scripts/config_whitelist.txt

@@ -293,7 +293,6 @@ CONFIG_CM922T_XA10
 CONFIG_CMDLINE_EDITING
 CONFIG_CMDLINE_PS_SUPPORT
 CONFIG_CMDLINE_TAG
-CONFIG_CMD_STRINGS
 CONFIG_CMD_SX151X
 CONFIG_CMD_TCA642X
 CONFIG_CMD_TERMINAL