Staging: comedi: serial2002: handle allocation failures on 'open'

The comedi device 'open' method for the serial2002 driver frees any old
'maxdata_list' and 'range_table_list' arrays belonging to a subdevice
and allocates them again, but was missing checks for allocation failure.

If an allocation fails, free the 'maxdata_list' and 'range_table_list'
arrays for all subdevices and return an error.

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