dev_get_regmap() return NULL and never return ERR_PTR().
check NULL to fix it.

Cc: stable@vger.kernel.org
Fixes: 672faa7bbf60 ("phy: phy-ocelot-serdes: add ability to be used in a non-syscon configuration")
Signed-off-by: Jinjie Ruan <redacted>
---
 drivers/phy/mscc/phy-ocelot-serdes.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/phy/mscc/phy-ocelot-serdes.c b/drivers/phy/mscc/phy-ocelot-serdes.c
index 1cd1b5db2ad7..77ca67ce6e91 100644
--- a/drivers/phy/mscc/phy-ocelot-serdes.c
+++ b/drivers/phy/mscc/phy-ocelot-serdes.c

@@ -512,8 +512,8 @@ static int serdes_probe(struct platform_device *pdev)
 						    res->name);
 	}
 
-	if (IS_ERR(ctrl->regs))
-		return PTR_ERR(ctrl->regs);
+	if (!ctrl->regs)
+		return -EINVAL;
 
 	for (i = 0; i < SERDES_MAX; i++) {
 		ret = serdes_phy_create(ctrl, i, &ctrl->phys[i]);

-- 
2.34.1