net: via: Fix wrong function name in comments

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

 drivers/net/ethernet/via/via-velocity.c:1908: warning: expecting prototype for tx_srv(). Prototype was for velocity_tx_srv() instead
 drivers/net/ethernet/via/via-velocity.c:2466: warning: expecting prototype for velocity_get_status(). Prototype was for velocity_get_stats() instead
 drivers/net/ethernet/via/via-velocity.c:3734: warning: expecting prototype for velocity_cleanup(). Prototype was for velocity_cleanup_module() instead

Cc: Francois Romieu <romieu@fr.zoreil.com>
Signed-off-by: Yang Shen <shenyang39@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>