of: unittest: move misplaced function declaration

The overlay_data_apply() declaration is outside of the #ifdef that contains
both the user and the definition, causing a compile-time warning in
some configurations:

drivers/of/unittest.c:48:19: error: 'overlay_data_apply' declared 'static' but never defined [-Werror=unused-function]
 static int __init overlay_data_apply(const char *overlay_name, int *overlay_id);

This moves the declaration into the #ifdef section.

Fixes: 39a751a4cb7e ("of: change overlay apply input data from unflattened to FDT")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Rob Herring <robh@kernel.org>

drivers/of/unittest.c

@@ -45,8 +45,6 @@ static struct unittest_results {
 	failed; \
 })
 
-static int __init overlay_data_apply(const char *overlay_name, int *overlay_id);
-
 static void __init of_unittest_find_node_by_name(void)
 {
 	struct device_node *np;
@@ -1192,6 +1190,7 @@ static int __init unittest_data_add(void)
 }
 
 #ifdef CONFIG_OF_OVERLAY
+static int __init overlay_data_apply(const char *overlay_name, int *overlay_id);
 
 static int unittest_probe(struct platform_device *pdev)
 {