drivers/net/r6040.c: Eliminate double sizeof

Taking sizeof the result of sizeof is quite strange and does not seem to be
what is wanted here.

This was fixed using the following semantic patch.
(http://www.emn.fr/x-info/coccinelle/

)

// <smpl>
@@
expression E;
@@

- sizeof (
  sizeof (E)
- )
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>