avcodec/h264_cabac: disable the unchecked bitstream reader for arm & aarch64

The newly added optimizations do not work with the unchecked reader
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/h264_cabac.c

@@ -26,7 +26,7 @@
  */
 
 #define CABAC(h) 1
-#define UNCHECKED_BITSTREAM_READER 1
+#define UNCHECKED_BITSTREAM_READER (!ARCH_ARM && !ARCH_AARCH64)
 
 #include "libavutil/attributes.h"
 #include "libavutil/timer.h"