uAMDC: review Ethernet PHY schematics

[npetersen2]

Per @psinha25 design review meeting for the uAMDC...

@ASHAD1 and @npetersen2 will review the electrical schematics for the Ethernet PHY on the uAMDC. We will use this issue to comment our findings.

The design that @psinha25 implemented comes from the STM32 development board (reference design). The schematics can be found at the end of this PDF -- note that they are very complex; we just care about the ethernet subsystem.

We should also cross-check @psinha25 schematics with the PHY datasheet to see if it seems reasonable. I bet if we just blindly copy the eval board (for schematics), it will probably work, but just to be safe, let's review the datasheet.