staging: comedi: adl_pci9118: absorb pci9118_ai_set_range_aref()

This function is called by the analog input (*insn_read) and (*do_cmd)
operations. The pci9118_set_chanlist() function is also called by those
operations. Setting the range and aref logically belongs with setting
the chanlist. To clarify the code, absorb pci9118_ai_set_range_aref()
into pci9118_set_chanlist().

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>