staging: lustre: fix lock imbalance

nrs_resource_put_safe() might hold a lock one one struct
while operating on the other.
There are 2 levels of structures.
Use nrs_policy_put(), which has locking baked in.

sparse gives the following warning:
drivers/staging/lustre//lustre/ptlrpc/nrs.c:498:39:
warning: context imbalance in 'nrs_resource_put_safe' -
  different lock contexts for basic block
Signed-off-by: Joshua Clayton <stillcompiling@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/ptlrpc/nrs.c

@@ -482,7 +482,6 @@ static void nrs_resource_get_safe(struct ptlrpc_nrs *nrs,
 static void nrs_resource_put_safe(struct ptlrpc_nrs_resource **resp)
 {
 	struct ptlrpc_nrs_policy *pols[NRS_RES_MAX];
-	struct ptlrpc_nrs *nrs = NULL;
 	int i;
 
 	for (i = 0; i < NRS_RES_MAX; i++) {
@@ -496,18 +495,9 @@ static void nrs_resource_put_safe(struct ptlrpc_nrs_resource **resp)
 	}
 
 	for (i = 0; i < NRS_RES_MAX; i++) {
-		if (pols[i] == NULL)
-			continue;
-
-		if (nrs == NULL) {
-			nrs = pols[i]->pol_nrs;
-			spin_lock(&nrs->nrs_lock);
-		}
-		nrs_policy_put_locked(pols[i]);
+		if (pols[i])
+			nrs_policy_put(pols[i]);
 	}
-
-	if (nrs != NULL)
-		spin_unlock(&nrs->nrs_lock);
 }
 
 /**