qlge: removing unreachable block of code

Currently the qlge_change_mtu() is never called if the new_mtu is
equal current MTU, due this condition on dev_set_mtu():

        if (new_mtu == dev->mtu)
                return 0;

So, this block of code is never reached and is being removed.

Signed-off-by: Breno Leitao <leitao@linux.vnet.ibm.com>
Signed-off-by: Ron Mercer <ron.mercer@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>