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

Drivers should not crash the kernel.

This function is only called by comedi_device_detach_cleanup() and the
s->minor will always be valid or the device wouldn't have attached in
the first place.

Leave the checks for safety in accessing the comedi_subdevice_minor_table
array but remove the BUG_ON() calls.

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>