Style: fix trailing spaces
diff --git a/programs/pkey/key_app_writer.c b/programs/pkey/key_app_writer.c
index ddd5e19..09233ff 100644
--- a/programs/pkey/key_app_writer.c
+++ b/programs/pkey/key_app_writer.c
@@ -84,7 +84,7 @@
     "    output_mode=private|public default: none\n"    \
     USAGE_OUT                                           \
     "\n"
- 
+
 #if !defined(POLARSSL_PK_WRITE_C) || !defined(POLARSSL_FS_IO)
 int main( void )
 {