clk: mediatek: clk-mt8173-apmixedsys: Fix return value for of_iomap() error

The of_iomap() function returns NULL in case of error so usage of
PTR_ERR() is wrong!
Change that to return -ENOMEM in case of failure.

Fixes: 41138fbf ("clk: mediatek: mt8173: Migrate to platform driver and common probe")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20230615122051.546985-3-angelogioacchino.delregno@collabora.comReviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Reviewed-by: Markus Schneider-Pargmann <msp@baylibre.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/mediatek/clk-mt8173-apmixedsys.c

@@ -148,7 +148,7 @@ static int clk_mt8173_apmixed_probe(struct platform_device *pdev)
 
 	base = of_iomap(node, 0);
 	if (!base)
-		return PTR_ERR(base);
+		return -ENOMEM;
 
 	clk_data = mtk_alloc_clk_data(CLK_APMIXED_NR_CLK);
 	if (IS_ERR_OR_NULL(clk_data))