stmicro: add more information to Kconfig

stmicro: add more information to Kconfig

This patch adds more info to stmicro' Kconfig files in order to be clearer
that the driver can be used by ethernet cards based on 10/100/1000/EQOS
Synopsys IP Cores.

EQOS was also added stmmac/Kconfig Kconfig, since dwmac4 is in fact EQoS,
one of Synopsys Ethernet IPs. More info at:
https://www.synopsys.com/dw/ipdir.php?ds=dwc_ether_qos

Signed-off-by: Joao Pinto <jpinto@synopsys.com>
Signed-off-by: David S. Miller <davem@davemloft.net>