staging: comedi: adl_pci9118: remove unnecessary check in check_channel_list()

staging: comedi: adl_pci9118: remove unnecessary check in check_channel_list()

Step 3 of the AI (*do_cmdtest) validates that the cmd->chanlist_len is >= 1. If
it's not the (*do_cmdtest) fails and check_channel_list() is never called. This
This function is also called by the AI (*do_cmd) and the comedi core ensures
that the async command has a valid chanlist. Remove the unnecessary 'n_chan'
check.

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>