Fix partial block encryption in cfb and ofb for s390x (legacy)

Fix partial block encryption in cfb and ofb for s390x (legacy)

Use the number of processed bytes information (num) from the generic
cipher context for the partial block handling in cfb and ofb also in
s390x-legacy code. For more details see 4df92c1a14 ("Fix partial block
encryption in cfb and ofb for s390x").

Signed-off-by: Holger Dengler <dengler@linux.ibm.com>
Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/23201)

(cherry picked from commit f9ccd209c3d121668c51a992613c698f2a774cb3)