convert the beta=0 branch to a for loop as well

kernel/generic/zgemm_beta.c

@@ -58,8 +58,8 @@ int CNAME(BLASLONG m, BLASLONG n, BLASLONG dummy1,
   c_offset = c;
 
   if (beta_r == 0. && beta_i == 0.) {
-    j = n;
-    do {
+    
+    for (j=n;j>0;j--) {
       c_offset1 = c_offset;
       c_offset += ldc;
 
@@ -88,8 +88,7 @@ int CNAME(BLASLONG m, BLASLONG n, BLASLONG dummy1,
 	  i--;
 	} while (i > 0);
       }
-      j --;
-    } while (j > 0);
+    }
 
   } else {