s390/crypto: Rework protected key AES for true asynch support

s390/crypto: Rework protected key AES for true asynch support

This is a complete rework of the protected key AES (PAES) implementation.
The goal of this rework is to implement the 4 modes (ecb, cbc, ctr, xts)
in a real asynchronous fashion:
- init(), exit() and setkey() are synchronous and don't allocate any
  memory.
- the encrypt/decrypt functions first try to do the job in a synchronous
  manner. If this fails, for example the protected key got invalid caused
  by a guest suspend/resume or guest migration action, the encrypt/decrypt
  is transferred to an instance of the crypto engine (see below) for
  asynchronous processing.
  These postponed requests are then handled by the crypto engine by
  invoking the do_one_request() callback but may of course again run into
  a still not converted key or the key is getting invalid. If the key is
  still not converted, the first thread does the conversion and updates
  the key status in the transformation context. The conversion is
  invoked via pkey API with a new flag PKEY_XFLAG_NOMEMALLOC.
  Note that once there is an active requests enqueued to get async
  processed via crypto engine, further requests also need to go via
  crypto engine to keep the request sequence.

This patch together with the pkey/zcrypt/AP extensions to support
the new PKEY_XFLAG_NOMEMMALOC should toughen the paes crypto algorithms
to truly meet the requirements for in-kernel skcipher implementations
and the usage patterns for the dm-crypt and dm-integrity layers.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Holger Dengler <dengler@linux.ibm.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Link: https://lore.kernel.org/r/20250514090955.72370-3-freude@linux.ibm.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>