Copied sys/dev/mmc/bridge.h to sys/cam/mmc/mmc_bus.h

There are lots of definitions I'm going to use for the new stack.
Define the new type for MMC transaction settings.

Using this structure MMC XPT will be able to tell MMC SIM
what bus parameters to set.
Refactor, move MMCIO handler to the separate function
Place the whole mmc_ios struct into trans_settings CCB for MMC
More debug output, minor style fixes.
More debug messages, longet timeout for callout.
Simplify init process, set MMC bus params.