avcodec/x86/cavsdsp: Put MMX code under mmx check

Without this the FPU state becomes trashed and causes mysterious
fate failures with cpuflags=0
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/x86/cavsdsp.c

@@ -565,7 +565,9 @@ av_cold void ff_cavsdsp_init_x86(CAVSDSPContext *c, AVCodecContext *avctx)
 {
     av_unused int cpu_flags = av_get_cpu_flags();
 
-    cavsdsp_init_mmx(c, avctx);
+    if (X86_MMX(cpu_flags))
+        cavsdsp_init_mmx(c, avctx);
+
 #if HAVE_AMD3DNOW_INLINE
     if (INLINE_AMD3DNOW(cpu_flags))
         cavsdsp_init_3dnow(c, avctx);