Add glue driver for Altera SOCFPGA Ethernet MAC (EMAC) found in
Terasic DE10-Pro (an Intel Stratix 10 GX/SX FPGA Development Kit).

The Altera EMAC is an instance of Synopsys DesignWare Gigabit MAC.

This driver sets correct clock range for MDIO interface on Intel Stratix 10
platform.

This is required due to lack of support for clock manager device for
this platform that could tell us the clock frequency value for ethernet
clock domain.

Sponsored by: DARPA, AFRL