arm64: ls1043ardb: Add distro secure boot support

Enable validation of boot.scr script prior to its execution dependent
on "secureboot" flag in environment. Disable fall back option to
nor/qspi boot in case of secure boot. Also enable "secureboot=y"
flag in environment for ARM based platforms instead of bootcmd.

Signed-off-by: Sumit Garg <sumit.garg@nxp.com>
Tested-by: Vinitha Pillai <vinitha.pillai@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>
diff --git a/configs/ls1043ardb_SECURE_BOOT_defconfig b/configs/ls1043ardb_SECURE_BOOT_defconfig
index d914be2..0fd0298 100644
--- a/configs/ls1043ardb_SECURE_BOOT_defconfig
+++ b/configs/ls1043ardb_SECURE_BOOT_defconfig
@@ -39,3 +39,4 @@
 CONFIG_RSA=y
 CONFIG_SPL_RSA=y
 CONFIG_RSA_SOFTWARE_EXP=y
+CONFIG_DISTRO_DEFAULTS=y