ice: do not add LLDP-specific filter if not necessary

Commit 34295a36 ("ice: implement new LLDP filter command")
introduced the ability to use LLDP-specific filter that directs all
LLDP traffic to a single VSI. However, current goal is for all trusted VFs
to be able to see LLDP neighbors, which is impossible to do with the
special filter.

Make using the generic filter the default choice and fall back to special
one only if a generic filter cannot be added. That way setups with "NVMs
where an already existent LLDP filter is blocking the creation of a filter
to allow LLDP packets" will still be able to configure software Rx LLDP on
PF only, while all other setups would be able to forward them to VFs too.

Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Rafal Romanowski <rafal.romanowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>