Fix dct32() compilation with --disable-yasm

Signed-off-by: NRonald S. Bultje <rsbultje@gmail.com>

libavcodec/x86/fft.c

@@ -56,11 +56,13 @@ av_cold void ff_fft_init_mmx(FFTContext *s)
 #if CONFIG_DCT
 av_cold void ff_dct_init_mmx(DCTContext *s)
 {
+#if HAVE_YASM
     int has_vectors = av_get_cpu_flags();
     if (has_vectors & AV_CPU_FLAG_AVX && HAVE_AVX)
         s->dct32 = ff_dct32_float_avx;
     else if (has_vectors & AV_CPU_FLAG_SSE && HAVE_SSE)
         s->dct32 = ff_dct32_float_sse;
+#endif
 }
 #endif