clk: renesas: rzg2l: Fix return value and unused assignment

Currently the function returns NULL on error, so exact error code is
lost.  This patch changes return convention of the function to use
ERR_PTR() on error instead.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Link: https://lore.kernel.org/r/1623896524-102058-1-git-send-email-yang.lee@linux.alibaba.com
[geert: Drop curly braces]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Author: Yang Li

drivers/clk/renesas/renesas-rzg2l-cpg.c

@@ -182,10 +182,8 @@ rzg2l_cpg_pll_clk_register(const struct cpg_core_clk *core,
 		return ERR_CAST(parent);
 
 	pll_clk = devm_kzalloc(dev, sizeof(*pll_clk), GFP_KERNEL);
-	if (!pll_clk) {
-		clk = ERR_PTR(-ENOMEM);
-		return NULL;
-	}
+	if (!pll_clk)
+		return ERR_PTR(-ENOMEM);
 
 	parent_name = __clk_get_name(parent);
 	init.name = core->name;