realtek: remove store_mcgroups/load_mcgroups

realtek: remove store_mcgroups/load_mcgroups

The current implementation only works when store and load are called for
the same port without any other calls in between. This is because the
store function only saves a single port number instead of a portmask for
each group. It also doesn't take into account that the allocation of
multicast group entries might change between store/load calls.

As a result, the multicast port mask table gets corrupted. This also
includes the reserved entry for unknown multicast, which gets corrupted
even when no other mdb entries have been added.

Remove the code for storing/loading multicast groups entirely, as the
original commit message doesn't offer a convincing reason why this would
be necessary in the first place.

Fixes: 724e4af530cd ("realtek: Store and Restore MC memberships for port enable/disable")
Signed-off-by: Jan Hoffmann <jan@3e8.eu>