fix(sdmmc): BDL calculate sectors cast fix

Closes https://github.com/espressif/esp-idf/issues/18875

components/sdmmc/include/esp_private/sdmmc_blockdev.h

@@ -0,0 +1,22 @@
+/*
+ * SPDX-FileCopyrightText: 2026 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#pragma once
+
+#include <stddef.h>
+#include <stdint.h>
+#include "esp_err.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+esp_err_t sdmmc_blockdev_calculate_sectors(size_t sector_size, uint64_t addr, size_t data_len,
+                                           size_t *out_start_sector_num, size_t *out_num_of_sectors);
+
+#ifdef __cplusplus
+}
+#endif