dvdnav: no need to check for 6 bytes before ps_pkt_size() anymore
dvdnav: no need to check for 6 bytes before ps_pkt_size() anymore

This mostly reverts commit 8a497301054ccc2d9d470ade60264036d43e3fc0.

jomanmuk/vlc-2.1,vlc-mirror/vlc,krichter722/vlc,jomanmuk/vlc-2.1,krichter722/vlc,vlc-mirror/vlc-2.1,xkfz007/vlc,vlc-mirror/vlc-2.1,vlc-mirror/vlc-2.1,krichter722/vlc,xkfz007/vlc,vlc-mirror/vlc-2.1,shyamalschandra/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc,krichter722/vlc,krichter722/vlc,jomanmuk/vlc-2.1,xkfz007/vlc,vlc-mirror/vlc-2.1,vlc-mirror/vlc-2.1,vlc-mirror/vlc,shyamalschandra/vlc,krichter722/vlc,jomanmuk/vlc-2.1,xkfz007/vlc,jomanmuk/vlc-2.2,xkfz007/vlc,jomanmuk/vlc-2.1,xkfz007/vlc,shyamalschandra/vlc,vlc-mirror/vlc,vlc-mirror/vlc,krichter722/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.2,xkfz007/vlc,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,vlc-mirror/vlc,jomanmuk/vlc-2.2,jomanmuk/vlc-2.1,vlc-mirror/vlc,shyamalschandra/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.1,shyamalschandra/vlc