ram: renesas: dbsc5: Fix JS1 index calculation

The JS1 index is calculated correctly, but the limiter cannot
be the max() function because the index should be lower than
JS1_USABLEC_SPEC_HI and the max() function would unconditionally
override the JS1 index to JS1_USABLEC_SPEC_HI. Use clamp() to
limit the JS1 index instead.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
diff --git a/drivers/ram/renesas/dbsc5/dram.c b/drivers/ram/renesas/dbsc5/dram.c
index 939775d..289d122 100644
--- a/drivers/ram/renesas/dbsc5/dram.c
+++ b/drivers/ram/renesas/dbsc5/dram.c
@@ -2192,7 +2192,7 @@
 		if (js1[i].fx3 * 2 * priv->ddr_mbpsdiv >= priv->ddr_mbps * 3)
 			break;
 
-	priv->js1_ind = max(i, JS1_USABLEC_SPEC_HI);
+	priv->js1_ind = clamp(i, 0, JS1_USABLEC_SPEC_HI);
 
 	priv->RL = js1[priv->js1_ind].RLset1;
 	priv->WL = js1[priv->js1_ind].WLsetA;