net: eth_designware: select PHYLIB in Kconfig

Select PHYLIB in drivers/net/Kconfig. And remove CONFIG_PHYLIB
from legacy board header files.

This fixed the warnings when both ALTERA_TSE and ETH_DESIGNWARE
are selected.

Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
Reported-by: Pavel Machek <pavel@denx.de>
Acked-by: Chin Liang See <clsee@altera.com>
Acked-by: Pavel Machek <pavel@denx.de>
Tested-by: Pavel Machek <pavel@denx.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>