Added patches to board/BeagleBone to improve mmc device enumeration,
and boot parameter initialization and device selection on omap
platforms for u-boot-2013.04.  With these patches, u-boot will
enumerate all mmc devices, even if there is an empty card slot, and on
omap platforms, if the boot device is an mmc device, the mmcdev
environment variable will be automatically set to that device, so that
MLO, bb-uboot and bbuldr are all loaded from the same device.