s390/zcrypt: support special flagged EP11 cprbs

Within an EP11 cprb there exists a byte field flags. Bit 0x20
of this field indicates a special cprb. A special cprb triggers
special handling in the firmware below the OS layer.

However, a special cprb also needs to have the S bit in GPR0
set when NQAP is called. This was not the case for EP11 cprbs
and this patch now introduces the code to support this.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>