usb: typec: anx7411: Fix return value check in anx7411_register_i2c_dummy_clients()

If i2c_new_dummy_device() fails, it never return NULL pointer, replace
NULL test with IS_ERR() to fix it.

Fixes: fe6d8a9c ("usb: typec: anx7411: Add Analogix PD ANX7411 support")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20220721071201.269344-2-yangyingliang@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/typec/anx7411.c

@@ -999,7 +999,7 @@ static int anx7411_register_i2c_dummy_clients(struct anx7411_data *ctx,
 			spi_addr = anx7411_i2c_addr[i].spi_address >> 1;
 			ctx->spi_client = i2c_new_dummy_device(client->adapter,
 							       spi_addr);
-			if (ctx->spi_client)
+			if (!IS_ERR(ctx->spi_client))
 				return 0;
 		}
 	}