secure_boot: enable chain of trust for ARM platforms

Chain of Trust is enabled for ARM platforms (LS1021 and LS1043).
In board_late_init(), fsl_setenv_chain_of_trust() is called which
will perform the following:
- If boot mode is non-secure, return (No Change)
- If boot mode is secure, set the following environmet variables:
   bootdelay = 0 (To disable Boot Prompt)
   bootcmd = CONFIG_CHAIN_BOOT_CMD (Validate and execute Boot script)

Signed-off-by: Aneesh Bansal <aneesh.bansal@nxp.com>
Acked-by: Ruchika Gupta <ruchika.gupta@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>
diff --git a/board/freescale/ls1021atwr/ls1021atwr.c b/board/freescale/ls1021atwr/ls1021atwr.c
index 8eaff5f..b85774c 100644
--- a/board/freescale/ls1021atwr/ls1021atwr.c
+++ b/board/freescale/ls1021atwr/ls1021atwr.c
@@ -30,6 +30,7 @@
 #ifdef CONFIG_U_QE
 #include "../../../drivers/qe/qe.h"
 #endif
+#include <fsl_validate.h>
 
 
 DECLARE_GLOBAL_DATA_PTR;
@@ -549,6 +550,9 @@
 #ifdef CONFIG_SCSI_AHCI_PLAT
 	ls1021a_sata_init();
 #endif
+#ifdef CONFIG_CHAIN_OF_TRUST
+	fsl_setenv_chain_of_trust();
+#endif
 
 	return 0;
 }