Set the trunk member of the mv88e6xxx_atu_entry structure regardless its
value, so that uninitialized structures gets the correct boolean value.

Note that no mainline code is affected by the current behavior.
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>