board: ti: am57xx: Enable CMD_DDR3

Enable CMD_DDR3 on all am57xx based platforms.
Signed-off-by: NLokesh Vutla <lokeshvutla@ti.com>

arch/arm/mach-omap2/omap5/Kconfig

@@ -39,6 +39,7 @@ config TARGET_AM57XX_EVM
 	select BOARD_LATE_INIT
 	select DRA7XX
 	select TI_I2C_BOARD_DETECT
+	select CMD_DDR3
 	imply SCSI
 	imply SPL_THERMAL
 	imply DM_THERMAL