Fix typo in platform macro defines for examples
diff --git a/programs/pkey/rsa_sign.c b/programs/pkey/rsa_sign.c
index c6c7905..b16fe5d 100644
--- a/programs/pkey/rsa_sign.c
+++ b/programs/pkey/rsa_sign.c
@@ -33,7 +33,7 @@
 #define mbedtls_fprintf         fprintf
 #define mbedtls_printf          printf
 #define mbedtls_snprintf        snprintf
-#define MBEDTLS_EXTI_SUCCESS    EXIT_SUCCESS
+#define MBEDTLS_EXIT_SUCCESS    EXIT_SUCCESS
 #define MBEDTLS_EXIT_FAILURE    EXIT_FAILURE
 #endif /* MBEDTLS_PLATFORM_C */