s390/zcrypt: Introduce CEX6 toleration

[ Upstream commit b3e8652bcbfa04807e44708d4d0c8cdad39c9215 ]

Signed-off-by: Harald Freudenberger <freude@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>