Add workaround for MCP61 Ethernet controller found on MSI K9
motherboard. PHY hardware used for the controller responded at
all possible addresses which in turn resulted in having 32 PHYs
for the controller. If driver detects "MSI K9N6PGM2-V2 (MS-7309)"
motherboard, tell miibus(4) PHY is located at 0.

Tested by: Chris H