1. change static emac-dma memory to dynamic
2. add esp_eth_deinit
3. modify ethernet example
4. add testcase for ethernet deinit function
5. GPIO0 could not output the 50MHz clock to PHY, so remove this configuration
1. The transmitting mode of the packets from LWIP to MAC is changed from synchronous to asynchronous.
2. The receive buf mode : support pointer mode and copy mode.
3. Add get phy status func used to config mac register.
