Trim down the Linux configuration some more
Reduce size of image so that it fits in 2 GB eMMC
beagleboneblack: u-boot updates

Pull uboot changes from Angstrom and RCN's uboot to
add support for eMMC. Also trimmed the u-boot configuration
down.

Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>