staging: comedi: comedi_buf: rename comedi_reset_async_buf()

For aesthetic reasons, rename this function to comedi_buf_reset(). This
makes all the asynchronous buffer functions have the same namespace.

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