[PATCH net-next] net: stmmac: fix missing unlock on error in stmmac_suspend()

['w00385741]

From: Wei Yongjun <weiyongjun1 at huawei.com>

Add the missing unlock before return from function
stmmac_suspend() in the error handling case.

Fixes: 5ec55823438e ("net: stmmac: add clocks management for gmac driver")
Reported-by: Hulk Robot <hulkci at huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1 at huawei.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index a10704d8e3c6..d50df998d3aa 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -5400,8 +5400,10 @@ int stmmac_suspend(struct device *dev)
 		/* Disable clock in case of PWM is off */
 		clk_disable_unprepare(priv->plat->clk_ptp_ref);
 		ret = pm_runtime_force_suspend(dev);
-		if (ret)
+		if (ret) {
+			mutex_unlock(&priv->lock);
 			return ret;
+		}
 	}
 	mutex_unlock(&priv->lock);