staging: comedi: mite: don't expose mite_dma_reset()

This function is only called by the mite driver. Remove the inline
function from the header and make it static in the driver.

Use the function in mite_prep_dma() instead of duplicating the code.

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>