refactor(spi_flash): move os layer to esp_mspi and chip configs to spi_flash

Also fixes the implicit dependency on esp_partition.

components/esp_mspi/linux/cache_utils.c

@@ -0,0 +1,12 @@
+/*
+ * SPDX-FileCopyrightText: 2026 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <stdbool.h>
+
+bool spi_flash_cache_enabled(void)
+{
+    return true;
+}