Used SwitchToThread for YIELDING on AMD piledriver with Windows.

Author: xianyi

common.h

@@ -315,9 +315,10 @@ typedef int blasint;
 #endif
 
 #ifdef PILEDRIVER
+#ifndef YIELDING
 #define YIELDING        __asm__ __volatile__ ("nop;nop;nop;nop;nop;nop;nop;nop;\n");
 #endif
-
+#endif
 
 #ifndef YIELDING
 #define YIELDING	sched_yield()