Fixed noisy warning with Clang

../common_thread.h:138:24: warning: equality comparison with extraneous parentheses [-Wparentheses-equality]
  if ((blas_cpu_number == 1)
       ~~~~~~~~~~~~~~~~^~~~
../common_thread.h:138:24: note: remove extraneous parentheses around the comparison to silence this warning
  if ((blas_cpu_number == 1)
      ~                ^   ~
../common_thread.h:138:24: note: use '=' to turn this equality comparison into an assignment
  if ((blas_cpu_number == 1)
                       ^~
                       =

common_thread.h

@@ -135,7 +135,7 @@ static __inline int num_cpu_avail(int level) {
 	int openmp_nthreads=0;
 #endif
 
-  if ((blas_cpu_number == 1) 
+  if (blas_cpu_number == 1
 
 #ifdef USE_OPENMP
       || omp_in_parallel()