CNB95: overflow: Add struct_size_t() and DEFINE_FLEX() helpers
JIRA: https://issues.redhat.com/browse/RHEL-30138
Commits:
d67790ddf0219a overflow: Add struct_size_t() helper
26dd68d293fd1c overflow: add DEFINE_FLEX() for on-stack allocs
Signed-off-by: Petr Oros poros@redhat.com