net/macb: fix misplaced call of free_netdev() in macb_remove()

fix a bug introduced by the multiqueue support patch:
"net/macb: add TX multiqueue support for gem"

the "bp" pointer to the netdev private data was dereferenced and used after the
associated memory had been freed by calling free_netdev().

Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>