lavu: Fix checkheaders for x86/emms.h

internal.h doesn't need to include cpu.h anymore since
the relevant code was moved to x86/emms.h

Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavutil/x86/emms.h

@@ -21,6 +21,7 @@
 
 #include "config.h"
 #include "libavutil/attributes.h"
+#include "libavutil/cpu.h"
 
 void avpriv_emms_yasm(void);