HSMMC: Build fixes for earlier patches

Build fixes for "HSMMC: Improve the interface for hsmmc_init()".
The header file needs to work without MMC support enabled, and
some board files needed to include it.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Tony Lindgren <tony@atomide.com>