test: Add tests for the extcon

Provide tests to the simple extcon device.

Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/extcon/Kconfig b/drivers/extcon/Kconfig
index 8a50250..6fd3d2b 100644
--- a/drivers/extcon/Kconfig
+++ b/drivers/extcon/Kconfig
@@ -12,4 +12,11 @@
 	  and to host USB ports. Many of 30-pin connectors including PDMI
 	  are also good examples.
 
+config EXTCON_SANDBOX
+	bool "Sandbox extcon"
+	depends on EXTCON
+	help
+	  Enable extcon support for sandbox. This is an emulation of a real
+	  extcon. Currectly all configuration is done in the probe.
+
 endmenu