refactor(rng): move rng read data function to rng_ll.h and update docs of RNG source

components/hal/esp32c2/include/hal/rng_ll.h

@@ -0,0 +1,24 @@
+/*
+ * SPDX-FileCopyrightText: 2026 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#pragma once
+
+#include <stdint.h>
+#include "soc/soc.h"
+#include "soc/syscon_reg.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+static inline uint32_t rng_ll_read_data(void)
+{
+    return REG_READ(RNG_DATA_REG);
+}
+
+#ifdef __cplusplus
+}
+#endif