cfg: add Netgear DG834v3 configuration

Change-Id: I3f4880d8b07b9623544b94d316b37e6d0ae97020
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/1189
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>