[hpsdr] Multiple Mercury operations

[Joe Martin K5SO]

All,

It is necessary with the new set of firmware that a jumper be placed  
across GPIO pins 2-3 (header J5 on Mercury).  Photos of the  
appropriate jumpers on Mercury J5 for multiple-Mercury operations are  
shown at

http://www.k5so.com/Clock%20connections.html

This jumper was not required before for multiple Mercury operation but  
it is required with the new firmware set.

73,  Joe K5SO