staging: comedi: adl_pci9111: change pci9111_fifo_reset into a function

This macro relies on a local variable having a specific name.
It's used multiple places so change it into a function.

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