Note that with WiFi stack enabled, system_init will reset frequency to 240MHz.
To make this setting useful, esp32-wifi-libs submodule needs to be updated.
1. timer reg file for both time group 0 and time group 1, not only timer group 0
2. fix bug that io mux header file mismatch with chip
3. fix bug that some BASE address not correct
4. add some static function to eagle.fpga32.rom.addr.v7.ld
5. add interrupts usage table
6. add some comments for rom code functions