Fix ret code in rsa_genkey.c
diff --git a/programs/pkey/rsa_genkey.c b/programs/pkey/rsa_genkey.c
index 9399217..1afec55 100644
--- a/programs/pkey/rsa_genkey.c
+++ b/programs/pkey/rsa_genkey.c
@@ -29,8 +29,11 @@
 #include "mbedtls/platform.h"
 #else
 #include <stdio.h>
-#define mbedtls_printf     printf
-#endif
+#include <stdlib.h>
+#define mbedtls_printf          printf
+#define MBEDTLS_EXTI_SUCCESS    EXIT_SUCCESS
+#define MBEDTLS_EXIT_FAILURE    EXIT_FAILURE
+#endif /* MBEDTLS_PLATFORM_C */
 
 #if defined(MBEDTLS_BIGNUM_C) && defined(MBEDTLS_ENTROPY_C) && \
     defined(MBEDTLS_RSA_C) && defined(MBEDTLS_GENPRIME) && \
@@ -61,7 +64,8 @@
 #else
 int main( void )
 {
-    int ret;
+    int ret = 1;
+    int exit_code = MBEDTLS_EXIT_FAILURE;
     mbedtls_rsa_context rsa;
     mbedtls_entropy_context entropy;
     mbedtls_ctr_drbg_context ctr_drbg;
@@ -105,14 +109,12 @@
         ( ret = mbedtls_rsa_export_crt( &rsa, &DP, &DQ, &QP ) )      != 0 )
     {
         mbedtls_printf( " failed\n  ! could not export RSA parameters\n\n" );
-        ret = 1;
         goto exit;
     }
 
     if( ( fpub = fopen( "rsa_pub.txt", "wb+" ) ) == NULL )
     {
         mbedtls_printf( " failed\n  ! could not open rsa_pub.txt for writing\n\n" );
-        ret = 1;
         goto exit;
     }
 
@@ -129,7 +131,6 @@
     if( ( fpriv = fopen( "rsa_priv.txt", "wb+" ) ) == NULL )
     {
         mbedtls_printf( " failed\n  ! could not open rsa_priv.txt for writing\n" );
-        ret = 1;
         goto exit;
     }
 
@@ -160,6 +161,8 @@
 */
     mbedtls_printf( " ok\n\n" );
 
+    exit_code = MBEDTLS_EXIT_SUCCESS;
+
 exit:
 
     if( fpub  != NULL )
@@ -180,7 +183,7 @@
     fflush( stdout ); getchar();
 #endif
 
-    return( ret );
+    return( exit_code );
 }
 #endif /* MBEDTLS_BIGNUM_C && MBEDTLS_ENTROPY_C && MBEDTLS_RSA_C &&
           MBEDTLS_GENPRIME && MBEDTLS_FS_IO && MBEDTLS_CTR_DRBG_C */