wmv2: Propagate the wmv2 idct permutation type to the dsputils context

This fixes encoding where the idct setting originally was set to
FF_IDCT_AUTO and dsputil chose a default idct with a non-null
permutation - even if the permutation tables were updated,
dct_quantize in x86/mpegvideoenc_template.c also checked the
value of this type variable.

Signed-off-by: Martin Storsjö <martin@martin.st>