Add MBEDTLS_PRIVATE wrapping to sample programs.

Signed-off-by: Mateusz Starzyk <mateusz.starzyk@mobica.com>
diff --git a/programs/pkey/rsa_decrypt.c b/programs/pkey/rsa_decrypt.c
index 1ba8c73..b13bb31 100644
--- a/programs/pkey/rsa_decrypt.c
+++ b/programs/pkey/rsa_decrypt.c
@@ -164,7 +164,7 @@
 
     fclose( f );
 
-    if( i != rsa.len )
+    if( i != rsa.MBEDTLS_PRIVATE(len) )
     {
         mbedtls_printf( "\n  ! Invalid RSA signature format\n\n" );
         goto exit;