board: ti: AM43XX: Add ddr voltage rail configuration

Add ddr voltage rail (dcdc3) configuration. Set the dcdc3
DDR supply to 1.35V.

Signed-off-by: Keerthy <j-keerthy@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
diff --git a/include/power/tps65218.h b/include/power/tps65218.h
index e3538e2..43b9c9a 100644
--- a/include/power/tps65218.h
+++ b/include/power/tps65218.h
@@ -63,6 +63,7 @@
 #define TPS65218_DCDC_VOLT_SEL_1200MV		0x23
 #define TPS65218_DCDC_VOLT_SEL_1260MV		0x29
 #define TPS65218_DCDC_VOLT_SEL_1330MV		0x30
+#define TPS65218_DCDC3_VOLT_SEL_1350MV		0x12
 
 #define TPS65218_CC_STAT	(BIT(0) | BIT(1))
 #define TPS65218_STATE		(BIT(2) | BIT(3))