lib: ecdsa: fix prevent memory leak in ecdsa_add_verify_data

- Ensure `free_ctx` is called in both error and success paths.
- Fix memory leak in `ctx.signature` when `do_add` fails."

Triggers found by static analyzer Svace.

Signed-off-by: Anton Moryakov <ant.v.moryakov@gmail.com>
1 file changed