soc: mediatek: mtk-svs: Use ULONG_MAX to compare floor frequency

The `freq` variable is of type unsigned long and, even though it does
currently work with u32 because no frequency is higher than U32_MAX,
it is not guaranteed that in the future we will see one.
Initialize the freq variable with ULONG_MAX instead of U32_MAX.

Link: https://lore.kernel.org/r/20231121125044.78642-18-angelogioacchino.delregno@collabora.com
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

drivers/soc/mediatek/mtk-svs.c

@@ -1804,7 +1804,7 @@ static int svs_bank_resource_setup(struct svs_platform *svsp)
 			return count;
 		}
 
-		for (i = 0, freq = U32_MAX; i < svsb->opp_count; i++, freq--) {
+		for (i = 0, freq = ULONG_MAX; i < svsb->opp_count; i++, freq--) {
 			opp = dev_pm_opp_find_freq_floor(svsb->opp_dev, &freq);
 			if (IS_ERR(opp)) {
 				dev_err(svsb->dev, "cannot find freq = %ld\n",