Add missing #ifdefs in aes.h
diff --git a/library/aes.c b/library/aes.c
index f516fba..fb211fe 100644
--- a/library/aes.c
+++ b/library/aes.c
@@ -982,6 +982,7 @@
     return( 0 );
 }
 #endif /* POLARSSL_CIPHER_MODE_CTR */
+
 #endif /* !POLARSSL_AES_ALT */
 
 #if defined(POLARSSL_SELF_TEST)