sandbox: Move CONFIG_IO_TRACE to Kconfig

This is only used on sandbox, so select it there.

Cc: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/common/Kconfig b/common/Kconfig
index 053e93e..8c71d3c 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -1086,3 +1086,6 @@
 	  These functions can be used by board to indicate to the OS
 	  the presence of the simple frame buffer with associated reserved
 	  memory
+
+config IO_TRACE
+	bool