net: lan966x: Allow to add rules in TCAM even if not enabled

The blamed commit implemented the vcap_operations to allow to add an
entry in the TCAM. One of the callbacks is to validate the supported
keysets. If the TCAM lookup was not enabled, then this will return
failure so no entries could be added.
This doesn't make much sense, as you can enable at a later point the
TCAM. Therefore change it such to allow entries in TCAM even it is not
enabled.

Fixes: 4426b78c

 ("net: lan966x: Add port keyset config and callback interface")
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>