[Fpga-synth] ARM & FPGA Audio board - update

[Eric Brombaugh]

I had an off-list discussion that convinced me a full MIDI port would  
be a good addition to the ARM & FPGA Audio board. I've replaced the  
generic 4-pin UART connector with a 6-pin header and appropriate drive/ 
receive circuitry. If the MIDI interface isn't needed the parts can be  
left off and jumpers installed to connect the raw serial signals to  
the header. Additionally, the 2nd UART available on the ARM MCU is  
brought out to the MISC IO header, so a raw serial port is available  
even when the MIDI port is in use.

The schematic & layout plot on the web page have been updated.  I'll  
be doing a final layout review and sending the board out for fab in a  
day or two.

Thanks for the feedback.

Eric