Ensure a safe margin between work arrays in the buffer even when GEMM_PQR is small

Author: martin-frbg

lapack/potrf/potrf_U_single.c

@@ -66,7 +66,7 @@ static FLOAT dm1 = -1.;
 #endif
 
 #define GEMM_PQ  MAX(GEMM_P, GEMM_Q)
-#define REAL_GEMM_R (GEMM_R - GEMM_PQ)
+#define REAL_GEMM_R (MAX(GEMM_R, GEMM_PQ + 96) - GEMM_PQ)
 
 #if 0
 #define SHARED_ARRAY