mv643xx_eth.c: remove unused txq_set_wrr()

The txq_set_wrr() function in drivers/net/mv643xx_eth.c is
unused, not even referenced under #if 0 or something like that,
which results in a compile-time warning:

drivers/net/mv643xx_eth.c:1070: warning: 'txq_set_wrr' defined but not used

Fix: remove it.

Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: David S. Miller <davem@davemloft.net>