s390/zcrypt: move cca misc functions to new code file

Rework of the pkey code. Moved all the cca generic code
away from pkey_api.c into a new file zcrypt_ccamisc.c.
This new file is now part of the zcrypt device driver
and exports a bunch of cca functions to pkey and may
be called from other kernel modules as well.

The pkey ioctl API is unchanged.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Ingo Franzki <ifranzki@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>