staging: comedi: addi_apci_3120: remove private data 'ui_EocEosConversionTime'

This driver tries to be tricky and allow passing an analog input conversion time
for the (*insn_read) in the (*insn_config).  The (*insn_config) doesn't follow
the comedi API and this programmable conversion time is not part of the API for
(*insn_read) operations.

Remove the member from the private data and use a fixed 10us (10000ns) conversion
time in the (*insn_read).

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>