staging: comedi: das08: No need to check insn->n for counter config

There is no need to check the value of `insn->n` is correct in
`das08_counter_config()` as the core comedi module will have already
checked it.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>