Extcon: Staticise extcon_class

It's not referenced outside the core file.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/extcon/extcon_class.c

@@ -65,7 +65,7 @@ const char *extcon_cable_name[] = {
 	NULL,
 };
 
-struct class *extcon_class;
+static struct class *extcon_class;
 #if defined(CONFIG_ANDROID)
 static struct class_compat *switch_class;
 #endif /* CONFIG_ANDROID */