clk: sp7021: fix return value check in sp7021_clk_probe()

devm_platform_ioremap_resource() never returns NULL pointer,
it will return ERR_PTR() when it fails, so replace the check
with IS_ERR().

Fixes: d54c1fd4a51e ("clk: Add Sunplus SP7021 clock driver")
Signed-off-by: Yang Yingliang <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Stephen Boyd <[e-mail]>

drivers/clk/clk-sp7021.c

···
 	int i;
 
 	clk_base = devm_platform_ioremap_resource(pdev, 0);
-	if (!clk_base)
-		return -ENXIO;
+	if (IS_ERR(clk_base))
+		return PTR_ERR(clk_base);
 	pll_base = devm_platform_ioremap_resource(pdev, 1);
-	if (!pll_base)
-		return -ENXIO;
+	if (IS_ERR(pll_base))
+		return PTR_ERR(pll_base);
 	sys_base = devm_platform_ioremap_resource(pdev, 2);
-	if (!sys_base)
-		return -ENXIO;
+	if (IS_ERR(sys_base))
+		return PTR_ERR(sys_base);
 
 	/* enable default clks */
 	for (i = 0; i < ARRAY_SIZE(sp_clken); i++)