staging: comedi: comedi_fops: remove BUG_ON() in comedi_cleanup()

The BUG_ON() checks in this function are not necessary.

comedi_cleanup_board_minors() clears all the entries in the
comedi_board_minor_table array and will call comedi_device_cleanup()
for all attached devices. comedi_device_cleanup() will then
clear the entries in the comedi_subdevice_minor_table array with
comedi_free_subdevice_minor().

Remove the BUG_ON(), drivers should not crash the kernel.

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>