avutil/x86/intmath: Disable use of tzcnt on older intel compilers.

ICC versions older than atleast 12.1.6 dont have the tzcnt intrinsics.
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Matt Oliver <protogonoi@gmail.com>

libavutil/x86/intmath.h

@@ -32,7 +32,7 @@
 #include "config.h"
 
 #if HAVE_FAST_CLZ
-#if defined(__INTEL_COMPILER) || defined(_MSC_VER)
+#if (defined(__INTEL_COMPILER) && (__INTEL_COMPILER>=1216)) || defined(_MSC_VER)
 #   if defined(__INTEL_COMPILER)
 #       define ff_log2(x) (_bit_scan_reverse((x)|1))
 #   else