boot: Kconfig: Disable non-FIT loading for TI secure devices

Non-FIT image loading support should be disabled for TI secure
devices as the image handlers for those image types do not follow
our secure boot checks.

Signed-off-by: Andrew Davis <afd@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/boot/Kconfig b/boot/Kconfig
index 4b0802b..9780473 100644
--- a/boot/Kconfig
+++ b/boot/Kconfig
@@ -405,7 +405,7 @@
 
 config LEGACY_IMAGE_FORMAT
 	bool "Enable support for the legacy image format"
-	default y if !FIT_SIGNATURE
+	default y if !FIT_SIGNATURE && !TI_SECURE_DEVICE
 	help
 	  This option enables the legacy image format. It is enabled by
 	  default for backward compatibility, unless FIT_SIGNATURE is