crypto: s390 - fix des and des3_ede ctr concurrency issue

crypto: s390 - fix des and des3_ede ctr concurrency issue

commit ee97dc7db4cbda33e4241c2d85b42d1835bc8a35 upstream.

In s390 des and 3des ctr mode there is one preallocated page
used to speed up the en/decryption. This page is not protected
against concurrent usage and thus there is a potential of data
corruption with multiple threads.

The fix introduces locking/unlocking the ctr page and a slower
fallback solution at 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>