net: dsa: don't unmask port bitmaps

The unapply functions are called on the error path.

As for dsa_port_mask, enabled_port_mask and cpu_port_mask won't be used
after so there's no need to unmask the corresponding port bit from them.

This makes dsa_cpu_port_unapply() and dsa_dsa_port_unapply() identical,
which can be factorized later.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>