sdio_slave_timing_t enum

Send at posedge, and sample at posedge. Default value for HS mode. If :c:macro:`SDIO_SLAVE_FLAG_HIGH_SPEED` is specified in :cpp:class:`sdio_slave_config_t`, this should be selected. Normally there's no problem using this to work in DS mode.

Send at negedge, and sample at posedge. Default value for DS mode and below. If :c:macro:`SDIO_SLAVE_FLAG_DEFAULT_SPEED` is specified in :cpp:class:`sdio_slave_config_t`, this should be selected.