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

The devm_kzalloc() function returns NULL on error, not error pointers.
Update the check to match.

Fixes: ebac87c ("clk: mmp: Add Marvell PXA1908 MPMU driver")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/5b3b963d-ecae-4819-be47-d82e8a58e64b@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-mpmu.c

@@ -78,8 +78,8 @@ static int pxa1908_mpmu_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))