* Demote the level of several debug messages to CAM_DEBUG_TRACE
* Add detection for SDHC cards that can do 1.8V. No voltage switch sequence
is issued yet;
* Don't create a separate LUN for each SDIO function. We need just one to make
pass(4) attach;
* Remove obsolete mmc_sdio* files. SDIO functionality will be moved into the
separate device that will manage a new sdio(4) bus;
* Terminate probing if got no reply to CMD0;
* Make bcm2835 SDHCI host controller driver compile with 'option MMCCAM'.
Approved by: imp (mentor)
Differential Revision: https://reviews.freebsd.org/D12109