fix: serial: add D-Cache invalidate in DMA RX path

[jiaoxy0]

On Cortex-M7 with D-Cache enabled, DMA writes to the RX ring buffer bypass the cache. When the CPU reads the buffer via rt_memcpy(), it may get stale cached data instead of the actual DMA-written content.

Add rt_hw_cpu_dcache_ops(RT_HW_CACHE_INVALIDATE) before each rt_memcpy() in _serial_dma_rx() to ensure cache coherence.

[github-actions]

📌 Code Review Assignment

🏷️ Tag: components

Reviewers: @Maihuanyi

Changed Files (Click to expand)

• components/drivers/serial/dev_serial.c

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📊 Current Review Status (Last Updated: 2026-07-24 00:06 CST)

• ⌛ @Maihuanyi Pending Review

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[github-actions]

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