Drop some unnecessary definitions

__x86_64__ and __AMD64__ should be already defined by the compiler to
specify the compilation target and shouldn't be defined manually.

I fixed two x86_64 checks to include VS variables, as removing this
might cause it to fail to compile on that compiler.

Signed-off-by: Jeremy Newton <Jeremy.Newton@amd.com>
Change-Id: I600ff449af85bf7d83ecab167d97933922e2d917

runtime/hsa-runtime/core/util/timer.h

@@ -145,7 +145,7 @@ class fast_clock {
   typedef uint64_t raw_rep;
   typedef double raw_frequency;
 
-#ifdef __x86_64__
+#if defined(__x86_64__) || defined(_M_X64)
   static __forceinline raw_rep raw_now() { return __rdtsc(); }
   static __forceinline raw_frequency raw_freq() { return freq; }
 #else