Update mmc dt node to use sdhci-omap binding instead of omap_hsmmcKeep me posted once the dependency gets merged.
I've also updated keystone_defconfig to enable CONFIG_MMC_SDHCI_OMAP.
Everyone who use a custom .config should also enable
CONFIG_MMC_SDHCI_OMAP for MMC to work.
This series should be merged only after 
 -> https://marc.info/?l=linux-kernel&m=152465820531802&w=2