package/dvbsnoop: fix musl build

Fixes
http://autobuild.buildroot.net/results/6fb/6fbe96af007803acfe9deacf26399cb19e5f2b47/
http://autobuild.buildroot.net/results/be6/be64a45ac158b9057fb3e7ef9b515250acc77187/


and many others

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>