- Split SDMMC page into pages about SDMMC/SDSPI hosts and a page about the protocol layer. - Use autogenerated API reference instead of manually generated one. - Add information about SDIO APIs.
Closes https://github.com/espressif/esp-idf/issues/1542, Closes https://github.com/espressif/esp-idf/issues/1008
Merges https://github.com/espressif/esp-idf/pull/1740