acl: correct acl vat help message
acl: correct acl vat help message

"ipv4"/"ipv6" option is not supported in acl_add_replace and
macip_acl_add_replace vat api.
Update its help message per actual api usage.

Type: fix

Change-Id: I8d34fac5f98bd78a46a5e98df05cd35182988dd8
Signed-off-by: Lijian Zhang <5bf702a4364390af4958a9b6773dbd5c19bc4226@arm.com>
Reviewed-by: Jieqiang Wang <db7a7d23988a26bd23c7608931deffc3581ce66a@arm.com>
Reviewed-by: Govindarajan Mohandoss <dbb1a59e1874dd3812d63a965eab6e17fe08c497@arm.com>

chrisy/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,FDio/vpp