crypto: mediatek - make symbol of_crypto_id static

Fixes the following sparse warning:

drivers/crypto/mediatek/mtk-platform.c:585:27: warning:
 symbol 'of_crypto_id' was not declared. Should it be static?
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/mediatek/mtk-platform.c

@@ -582,7 +582,7 @@ static int mtk_crypto_remove(struct platform_device *pdev)
 	return 0;
 }
 
-const struct of_device_id of_crypto_id[] = {
+static const struct of_device_id of_crypto_id[] = {
 	{ .compatible = "mediatek,eip97-crypto" },
 	{},
 };