staging: comedi: addi_apci_3120: absorb apci3120_ai_reset_fifo()

This function is only called by apci3120_set_chanlist(). Absorb it.

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>