net: lan966x: Add VCAP debugFS support

Enable debugfs for vcap for lan966x. This will allow to print all the
entries in the VCAP and also the port information regarding which keys
are configured.

Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>