staging: most: net: remove useless variable channels_opened

The function most_nd_stop is only called by successful return from the
function most_nd_open, so the channels_opened is always true in the
function most_nd_stop.

The functions aim_resume_tx_channel and aim_rx_data are only called
after successful most_start_channel in the function most_nd_open, so the
channels_opened is always true in the functions aim_resume_tx_channel
and aim_rx_data.

Signed-off-by: Andrey Shvetsov <andrey.shvetsov@k2l.de>
Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>