net: chelsio: cxgb4: Fix wrong function name in comments

Fixes the following W=1 kernel build warning(s):

 drivers/net/ethernet/chelsio/cxgb3/sge.c:677: warning: expecting prototype for free_qset(). Prototype was for t3_free_qset() instead
 drivers/net/ethernet/chelsio/cxgb3/sge.c:1266: warning: expecting prototype for eth_xmit(). Prototype was for t3_eth_xmit() instead

Cc: Raju Rangoju <rajur@chelsio.com>
Signed-off-by: Yang Shen <shenyang39@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>