crypto: s390 - fix concurrency issue in aes-ctr mode

crypto: s390 - fix concurrency issue in aes-ctr mode

commit 0519e9ad89e5cd6e6b08398f57c6a71d9580564c upstream.

The aes-ctr mode uses one preallocated page without any concurrency
protection. When multiple threads run aes-ctr encryption or decryption
this can lead to data corruption.

The patch introduces locking for the page and a fallback solution with
slower en/decryption performance in concurrency situations.

Signed-off-by: Harald Freudenberger <freude@linux.vnet.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>