binman: Add support for TEE BL32

Add an entry for OP-TEE Trusted OS 'BL32' payload.
This is required by platforms using Cortex-A cores with TrustZone
technology.

Signed-off-by: Roger Quadros <rogerq@kernel.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Add missing-blob-help, renumber the test file, update entry-docs:
Signed-off-by: Simon Glass <sjg@chromium.org>