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/arch/arm/cpu/armv8/fsl-layerscape/soc.c b/arch/arm/cpu/armv8/fsl-layerscape/soc.c
index 23d6b73..d97a445 100644
--- a/arch/arm/cpu/armv8/fsl-layerscape/soc.c
+++ b/arch/arm/cpu/armv8/fsl-layerscape/soc.c
@@ -12,6 +12,9 @@
 #include <asm/io.h>
 #include <asm/global_data.h>
 #include <asm/arch-fsl-layerscape/config.h>
+#ifdef CONFIG_CHAIN_OF_TRUST
+#include <fsl_validate.h>
+#endif
 
 DECLARE_GLOBAL_DATA_PTR;
 
@@ -241,6 +244,9 @@
 #ifdef CONFIG_SCSI_AHCI_PLAT
 	sata_init();
 #endif
+#ifdef CONFIG_CHAIN_OF_TRUST
+	fsl_setenv_chain_of_trust();
+#endif
 
 	return 0;
 }