Use the two-operand form of DCBT on all PPC970 regardless of OS

There seems to be no advantage to the three-operand form used in the earliest GotoBLAS kernels, and it causes compilation problems  on other than the previously special-cased platforms as well

common_power.h

@@ -241,7 +241,7 @@ static inline int blas_quickdivide(blasint x, blasint y){
 #define HAVE_PREFETCH
 #endif
 
-#if defined(POWER3) || defined(POWER6) || defined(PPCG4) || defined(CELL) || defined(POWER8) || defined(POWER9) || ( defined(PPC970) && ( defined(OS_DARWIN) || defined(OS_FREEBSD) ) )
+#if defined(POWER3) || defined(POWER6) || defined(PPCG4) || defined(CELL) || defined(POWER8) || defined(POWER9) || defined(PPC970)
 #define DCBT_ARG	0
 #else
 #define DCBT_ARG	8