Earthmate LT-20 devices (both "old" and "new" versions) can't tolerate
a GET_CONFIG command.  The original Earthmate has no trouble with
this.  Presumably other non-Earthmate devices are still OK as well.
This change disables the use of GET_CONFIG for cases where it is known
not to work.
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>