Convert CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/common/Kconfig b/common/Kconfig
index e78e918..69d09ec 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -309,6 +309,15 @@
 	  environment variables can be updated after boot to change the
 	  input/output devices.
 
+config SYS_CONSOLE_OVERWRITE_ROUTINE
+	bool "Allow board control over console overwriting"
+	help
+	  If this is enabled, and the board-specific function
+	  overwrite_console() returns 1, the stdin, stderr and stdout are
+	  switched to the serial port, else the settings in the environment
+	  are used. If this is not enabled, the console will not be switched
+	  to serial.
+
 config SYS_CONSOLE_ENV_OVERWRITE
 	bool "Update environment variables during console init"
 	help