staging: comedi: me4000: don't clobber command flags

The low-level Comedi drivers shouldn't change the `flags` member of
`struct comedi_cmd` as the Comedi core also uses some of those flags.
They should just ignore the flags they don't understand.

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