tests/fate/libavcodec: fate-idct8x8 needs dct

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

tests/fate/libavcodec.mak

@@ -3,7 +3,7 @@ fate-golomb: libavcodec/golomb-test$(EXESUF)
 fate-golomb: CMD = run libavcodec/golomb-test
 fate-golomb: REF = /dev/null
 
-FATE_LIBAVCODEC-yes += fate-idct8x8
+FATE_LIBAVCODEC-$(CONFIG_DCT) += fate-idct8x8
 fate-idct8x8: libavcodec/dct-test$(EXESUF)
 fate-idct8x8: CMD = run libavcodec/dct-test -i
 fate-idct8x8: CMP = null