powercap/dtpm: Move the 'root' reset place

The 'root' node is checked everytime a dtpm node is destroyed.

When we reach the end of the hierarchy destruction function, we can
unconditionnaly set the 'root' node to NULL again.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20220130210210.549877-5-daniel.lezcano@linaro.org

drivers/powercap/dtpm.c

@@ -184,9 +184,6 @@ int dtpm_release_zone(struct powercap_zone *pcz)
 	else
 		kfree(dtpm);
 
-	if (root == dtpm)
-		root = NULL;
-
 	return 0;
 }
 
@@ -656,6 +653,8 @@ void dtpm_destroy_hierarchy(void)
 
 	pct = NULL;
 
+	root = NULL;
+
 out_unlock:
 	mutex_unlock(&dtpm_lock);
 }