KVM: s390: Use fallthrough;

Convert the various uses of fallthrough comments to fallthrough;

Done via script
Link: https://lore.kernel.org/lkml/b56602fcf79f849e733e7b521bb0e17895d390fa.1582230379.git.joe@perches.com



Signed-off-by: Joe Perches <joe@perches.com>
Link: https://lore.kernel.org/r/d63c86429f3e5aa806aa3e185c97d213904924a5.1583896348.git.joe@perches.com


[borntrager@de.ibm.com: Fix link to tool and subject]
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>