WIDGET: Handle widgets which can go negative, but where the IIO
attribute should be the abs value of this.

Signed-off-by: Robin Getz <Robin.Getz@analog.com>
FMCOMMS2: update the plugin/glade file with a more readable text,
          which is split between Tx and things inside the FPGA, to
          try to make it a little more clear.

Signed-off-by: Robin Getz <Robin.Getz@analog.com>
SAVE AS: Don't warn and fail, when you don't need to.

Signed-off-by : Robin Getz <Robin.Getz@analog.com>