net: dsa: felix: Annotate struct action_gate_entry with __counted_by

Add the __counted_by compiler attribute to the flexible array member
entries to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
CONFIG_FORTIFY_SOURCE.

Signed-off-by: Hongbo Li <lihongbo22@huawei.com>
Link: https://patch.msgid.link/20240904014956.2035117-1-lihongbo22@huawei.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>