Unlike other list types, enum wasn't adding any padding, which caused
a mismatch between the generated struct size and GenericList struct
size. More details in a678e26c

This crashed qemu if calling qmp query-tpm-types for example, which
upsets libvirt capabilities probing. Reproducer on i686:

(sleep 5; printf '{"execute":"qmp_capabilities"}\n{"execute":"query-tpm-types"}\n') | ./i386-softmmu/qemu-system-i386 -S -nodefaults -nographic -M none -qmp stdio

https://bugs.launchpad.net/qemu/+bug/1219207

Cc: qemu-stable@nongnu.org
Signed-off-by: NCole Robinson <crobinso@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Tested-by: NRichard W.M. Jones <rjones@redhat.com>
Signed-off-by: NLuiz Capitulino <lcapitulino@redhat.com>
(cherry picked from commit 02dc4bf5)
Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>