SP int: define errors for backward compatability

wolfssl/wolfcrypt/sp_int.h

@@ -666,6 +666,7 @@ typedef struct sp_ecc_ctx {
 /** Result of comparison is that the first number is less than second. */
 #define MP_LT    -1
 
+/* ERROR VALUES */
 /** Error value on success. */
 #define MP_OKAY          0
 /** Error value when dynamic memory allocation fails. */
@@ -676,6 +677,10 @@ typedef struct sp_ecc_ctx {
  * completion.
  */
 #define FP_WOULDBLOCK   -4
+/* Unused error. Defined for backward compatability. */
+#define MP_NOT_INF      -5
+/* Unused error. Defined for backward compatability. */
+#define MP_RANGE        MP_NOT_INF
 
 /* Number of bits in each word/digit. */
 #define DIGIT_BIT  SP_WORD_SIZE