netperf: enable demo mode

Enable demo mode for netperf to activates a global "-D" <interval> option.
This option will display interim results at least every time interval.

Signed-off-by: Kelvin Cheung <keguang.zhang@gmail.com>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/netperf/netperf.mk

@@ -7,6 +7,7 @@
 NETPERF_VERSION = 2.6.0
 NETPERF_SITE = ftp://ftp.netperf.org/netperf
 NETPERF_CONF_ENV = ac_cv_func_setpgrp_void=set
+NETPERF_CONF_OPT = --enable-demo=yes
 NETPERF_LICENSE = netperf license
 NETPERF_LICENSE_FILES = COPYING