Allow encoder ratio to be negative

[kmpeters]

A change was made to the motor record to allow the sign of the encoder ratio to be preserved:

https://github.com/epics-modules/motor/pull/84/files

And devOmsCom.cc was modified to retain the original behavior, which ignored the sign of the encoder ratio:

https://github.com/epics-modules/motor/pull/98/files

The issue was original discussed here:

epics-modules/motor#82

Setting the ERES to a negative value currently results in the motor being commanded to move in the wrong direction. Reverting the change to devOmsCom.cc in motor pull request 98 should resolve the issue, assuming the UU command accepts negative arguments.