Staging: comedi: serial2002: decrease stack usage

512 bytes of stack can be saved in serial_2002_open() by modifying
'struct config_t'.  A short int suffices for the 'kind' and 'bits'
members.  (Actually, a char would suffice, but wouldn't save any more
stack than a short int.)

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