ice: Remove ucast_shared

Remove ucast_shared as it was always true. Remove the code depending on
ucast_shared from ice_add_mac and ice_remove_mac.
Remove ice_find_ucast_rule_entry function as it was only
used when ucast_shared was set to false.

Signed-off-by: Sylwester Dziedziuch <sylwesterx.dziedziuch@intel.com>
Signed-off-by: Jedrzej Jagielski <jedrzej.jagielski@intel.com>
Tested-by: Gurucharan <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>