clk: mmp: pxa1908-apbcp: Fix a NULL vs IS_ERR() check

The devm_kzalloc() function doesn't return error pointers, it returns
NULL on error.  Update the check to match.

Fixes: a89233d ("clk: mmp: Add Marvell PXA1908 APBCP driver")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/6155067d-aed5-4799-9e14-6dff7be1cb3a@stanley.mountain
Acked-by: Duje Mihanović <duje.mihanovic@skole.hr>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

Author: Dan Carpenter

drivers/clk/mmp/clk-pxa1908-apbcp.c

@@ -48,8 +48,8 @@ static int pxa1908_apbcp_probe(struct platform_device *pdev)
 	struct pxa1908_clk_unit *pxa_unit;
 
 	pxa_unit = devm_kzalloc(&pdev->dev, sizeof(*pxa_unit), GFP_KERNEL);
-	if (IS_ERR(pxa_unit))
-		return PTR_ERR(pxa_unit);
+	if (!pxa_unit)
+		return -ENOMEM;
 
 	pxa_unit->base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(pxa_unit->base))