USB: garmin_gps support for new generation of gps receivers

The attached patch adds support for the new generation of gps receivers (eg. 
GPSmap 60Cx) to garmin_gps.c.
Signed-off-by: Hermann Kneissel <herkne@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>