multimedia/libdvbcsa: Update MASTER_SITES

Use VideoLAN's CDN as primary site and fallback to download.videolan.org
Remove dead mirror and while at it switch to DISTVERSION for consistency

Reference: http://get.videolan.org/libdvbcsa/1.1.0/libdvbcsa-1.1.0.tar.gz?mirrorlist

PR: 270057
Reviewed by: decke (maintainer)