s390/zcrypt: use fallthrough;

s390/zcrypt: use fallthrough;

BugLink: https://bugs.launchpad.net/bugs/1939618
Convert the various uses of fallthrough comments to fallthrough;

Done via script
Link: https://lore.kernel.org/lkml/b56602fcf79f849e733e7b521bb0e17895d390fa.1582230379.git.joe.com/
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
(cherry picked from commit fcf0220abc5b65d12ff48ba9870cf3d90801b075)
Signed-off-by: Frank Heimes <frank.heimes@canonical.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>