tg3: Integrate flowctrl check into AN adv check

This patch integrates tg3_adv_1000T_flowctrl_ok() into
tg3_copper_is_advertising_all() and renames the function
tg3_phy_copper_an_config_ok().

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Reviewed-by: Michael Chan <mchan@broadcom.com>
Reviewed-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>