avcodec/jpeg2000dec: Use 32x32->64bit for 9/7i dequantization

Like the 5/3 case this is needed to avoid overflows and similarly for 16bpp
output pure 32bit operations are insufficient if high quality is wanted

Note, this code-path is only used in bitexact mode, so this should not
affect the speed of any real use-case

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
