Convert CONFIG_CMD_CLK to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_CLK

Signed-off-by: Simon Glass <sjg@chromium.org>
[trini: imply CMD_CLK on ARCH_ZYNQ]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index 7a12441..9eb6a35 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -387,6 +387,15 @@
 
 menu "Device access commands"
 
+config CMD_CLK
+	bool "clk - Show clock frequencies"
+	help
+	  (deprecated)
+	  Shows clock frequences by calling a sock_clk_dump() hook function.
+	  This is depreated in favour of using the CLK uclass and accessing
+	  clock values from associated drivers. However currently no command
+	  exists for this.
+
 config CMD_DM
 	bool "dm - Access to driver model information"
 	depends on DM