drivers/net: drop redundant memset

The region set by the call to memset is immediately overwritten by the
subsequent call to memcpy.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/

)

// <smpl>
@@
expression e1,e2,e3,e4;
@@

- memset(e1,e2,e3);
  memcpy(e1,e4,e3);
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: David S. Miller <davem@davemloft.net>