net: lan966x: Add port keyset config and callback interface

Implement vcap_operations and enable default port keyset configuration
for each port. Now it is possible actually write/read/move entries in
the VCAP.
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>