power: pm8921-charger: decrease the index by 1 except for case 0

The purpose is to get index of [0..3] instead of [0..4].

Change-Id: I736312f04edbd889ac325fe8d0180f9a38c816ca
Signed-off-by: Willie Ruan <wruan@codeaurora.org>
diff --git a/drivers/power/pm8921-charger.c b/drivers/power/pm8921-charger.c
index bbe5de7..68f4bdd 100644
--- a/drivers/power/pm8921-charger.c
+++ b/drivers/power/pm8921-charger.c
@@ -2904,6 +2904,9 @@
 			break;
 	}
 
+	if (i > 0)
+		i--;
+
 	return ibatmax_adj_table[i].max_adj_ma;
 }