avcodec/jpeg2000dec: Check for duplicate SIZ marker

      Fixes: 0231a17345734228011c6f35a64e4594/asan_heap-oob_1d92a72_3218_1213809a9e3affec77e4c191fdfdc0a9.mov

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>