nvmem: hide unused nvmem_find_cell_by_index function

nvmem_find_cell_by_index() is only called from inside an #ifdef,
so we get a build warning without CONFIG_OF:

drivers/nvmem/core.c:496:1: error: 'nvmem_find_cell_by_index' defined but not used [-Werror=unused-function]

Move it into the same #ifdef as the caller to avoid the warning.

Fixes: e888d445 ("nvmem: resolve cells from DT at registration time")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/core.c

@@ -493,22 +493,6 @@ static int nvmem_add_cells_from_table(struct nvmem_device *nvmem)
 	return rval;
 }
 
-static struct nvmem_cell *
-nvmem_find_cell_by_index(struct nvmem_device *nvmem, int index)
-{
-	struct nvmem_cell *cell = NULL;
-	int i = 0;
-
-	mutex_lock(&nvmem_mutex);
-	list_for_each_entry(cell, &nvmem->cells, node) {
-		if (index == i++)
-			break;
-	}
-	mutex_unlock(&nvmem_mutex);
-
-	return cell;
-}
-
 static struct nvmem_cell *
 nvmem_find_cell_by_name(struct nvmem_device *nvmem, const char *cell_id)
 {
@@ -975,6 +959,22 @@ nvmem_cell_get_from_lookup(struct device *dev, const char *con_id)
 }
 
 #if IS_ENABLED(CONFIG_OF)
+static struct nvmem_cell *
+nvmem_find_cell_by_index(struct nvmem_device *nvmem, int index)
+{
+	struct nvmem_cell *cell = NULL;
+	int i = 0;
+
+	mutex_lock(&nvmem_mutex);
+	list_for_each_entry(cell, &nvmem->cells, node) {
+		if (index == i++)
+			break;
+	}
+	mutex_unlock(&nvmem_mutex);
+
+	return cell;
+}
+
 /**
  * of_nvmem_cell_get() - Get a nvmem cell from given device node and cell id
  *