libmp4: Move variable declaration to avoid unused variable warning
libmp4: Move variable declaration to avoid unused variable warning

demux/mp4/libmp4.c:858:12: warning: variable ‘translate’ set but not used [-Wunused-but-set-variable]

Signed-off-by: Jean-Baptiste Kempf <7b85a41a628204b76aba4326273a3ccc74bd009a@videolan.org>

shyamalschandra/vlc,krichter722/vlc,krichter722/vlc,vlc-mirror/vlc,krichter722/vlc,krichter722/vlc,xkfz007/vlc,shyamalschandra/vlc,krichter722/vlc,xkfz007/vlc,xkfz007/vlc,vlc-mirror/vlc,krichter722/vlc,xkfz007/vlc,vlc-mirror/vlc,vlc-mirror/vlc,shyamalschandra/vlc,shyamalschandra/vlc,vlc-mirror/vlc,vlc-mirror/vlc,vlc-mirror/vlc,shyamalschandra/vlc,xkfz007/vlc,xkfz007/vlc,krichter722/vlc,shyamalschandra/vlc,xkfz007/vlc,shyamalschandra/vlc