lib: rsa: check algo match in rsa_verify_with_keynode

The algo name should match between the FIT's signature node and the
U-Boot's control FDT.

If we do not check it, U-Boot's control FDT can expect sha512 hash but
nothing will prevent to accept image with sha1 hash if the signature is correct.

Signed-off-by: Matthieu CASTET <castet.matthieu@free.fr>