vfi/x86/vf_idet: fix incorrect use of paddq

paddq is an SSE2 instruction so it cannot be used for MMX.

This was probably just a typo because the sums are dwords anyway.

Reviewed-by: Pascal Massimino <pascal.massimino@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>