1. add kconfig help for GPIO0 output mode
2. fix a bug when select gpio0 output mode and initialize psram
3. make default config to official development board
4. fix wrong LAN8720 register index
1. Original register mapping for LAN8720 has some registers that doesn't exist/support.
So just remove them, and fix the power and init function for LAN8720.
2. GPIO16 and GPIO17 is occupied by PSRAM, so only ETH_CLOCK_GPIO_IN mode is supported in that case if using PSRAM.
3. Fix bug of OTA failing with Ethernet
4. Fix bug of multicast with Ethernet
5. Fix potential memory leak