SILABS port: fix sizeof

A sizeof wasn't dereferencing a pointer using the sizeof the pointer and
not the actual struct. This is limited to setting the key for an AES
operation only when using SILABS SE2 acceleration.

wolfcrypt/src/port/silabs/silabs_aes.c

@@ -48,7 +48,7 @@ int wc_AesSetKey(Aes* aes, const byte* userKey, word32 keylen,
         return BUFFER_E;
     }
 
-    XMEMSET(aes, 0, sizeof(aes));
+    XMEMSET(aes, 0, sizeof(*aes));
 
     if (keylen > sizeof(aes->key)) {
         return BAD_FUNC_ARG;