fix(openthread): fix SPI host-RCP communication loss

- 1. H2 SPI slave DMA transaction length insufficient for CMD_RESET
  frame
- 2. H2 SPI slave BUSY race at boot causing permanent deadlock
- 3. H2 INT pin spurious NEGEDGE on chip reset
- 4. H2 SPI slave trans_len exceeding buffer size
- 5. S3 host RST flag handling preventing Spinel-layer reset detection
- 6. S3 stale eventfd events after HardwareReset causing WaitResponse
  timeout
- 7. ot_br missing coprocessor reset failure callback

components/openthread/private_include/esp_spi_spinel_interface.hpp

@@ -168,6 +168,7 @@ private:
 
     esp_openthread_spi_host_config_t m_spi_config;
     uint8_t m_tx_buffer[kSPIFrameSize];
+    uint8_t *m_rx_dma_buf; ///< DMA-aligned RX buffer; avoids cache-coherency issues with unaligned frame buffer
     int m_event_fd;
     volatile uint16_t m_pending_data_len;