ice: Clear synchronized addrs when adding VFs in switchdev mode

When spawning VFs in switchdev mode, internal filter list of VSIs is
cleared, which includes MAC rules. However MAC entries stay on netdev's
multicast list, which causes error message when bringing link up after
spawning VFs ("Failed to delete MAC filters"). __dev_mc_sync() is
called and tries to unsync addresses that were already removed
internally when adding VFs.

This can be reproduced with:
1) Load ice driver
2) Change PF to switchdev mode
3) Bring PF link up
4) Bring PF link down
5) Create a VF on PF
6) Bring PF link up

Added clearing of netdev's multicast (and also unicast) list when
spawning VFs in switchdev mode, so the state of internal rule list and
netdev's MAC list is consistent.

Fixes: 1a1c40df

 ("ice: set and release switchdev environment")
Signed-off-by: Marcin Szycik <marcin.szycik@linux.intel.com>
Tested-by: Sandeep Penigalapati <sandeep.penigalapati@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>