8.25. Removal of deprecated CONFIG_BOOTM_OPTEE

The support for late loading of OP-TEE had been deprecated and ultimately removed as it greatly increased the attack surface and was only supported on 32-bit ARM systems.

OP-TEE loading is now only supported in the prebootloader.

For i.MX6 boards, this can be enabled by enabling CONFIG_FIRMWARE_IMX6_OPTEE.

8.26. sha1 no longer accepted for secure boot

FIT images using sha1 are no longer accepted as secure boot images. sha1 has been proven insecure in 2017.