ethernet: fix some bugs in phy&mac driver

ethernet: fix some bugs in phy&mac driver

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

Closes https://github.com/espressif/esp-idf/issues/2564
Closes https://github.com/espressif/esp-idf/issues/2620
Closes https://github.com/espressif/esp-idf/issues/2657