multimedia/libdvbpsi: Update MASTER_SITES

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

Reference: http://get.videolan.org/libdvbpsi/1.3.3/libdvbpsi-1.3.3.tar.bz2?mirrorlist

PR: 270149
Approved by: multimedia (riggs)