s390/zcrypt: code cleanup

This patch tries to fix as much as possible of the
checkpatch.pl --strict findings:
  CHECK: Logical continuations should be on the previous line
  CHECK: No space is necessary after a cast
  CHECK: Alignment should match open parenthesis
  CHECK: 'useable' may be misspelled - perhaps 'usable'?
  WARNING: Possible repeated word: 'is'
  CHECK: spaces preferred around that '*' (ctx:VxV)
  CHECK: Comparison to NULL could be written "!msg"
  CHECK: Prefer kzalloc(sizeof(*zc)...) over kzalloc(sizeof(struct...)...)
  CHECK: Unnecessary parentheses around resp_type->work
  CHECK: Avoid CamelCase: <xcRB>

There is no functional change comming with this patch, only
code cleanup, renaming, whitespaces, indenting, ... but no
semantic change in any way. Also the API (zcrypt and pkey
header file) is semantically unchanged.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Jürgen Christ <jchrist@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>