Works for 3.3V eMMC in 4 line mode.
Not implemented:
- DDR mode for SD cards (UHS-I) also need voltage to be switched to 1.8V.
- 8-line DDR mode for eMMC to be implemented later.
- Add SDIO support at protocol layer (probing, data transfer, interrupts)
- Add SDIO interrupts support in SDMMC host
- Add test (communicate with ESP32 in SDIO download mode)