avcodec/diracdec: Fix qfactor/offset tables

It seems the previous tables where calculated with 32bit integers ignoring
overflows.
Also check for the max qindex, the value is choosen so that the qfactor/offset
fit in int32.

Fixes: 070b7914fd5dfe8f93248bea71363410/asan_static-oob_c8d034_2764_258e20f4a3c79158aecddb61a833d756.drc
Fixes out of array reads

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