arm: Add config and sources for Beagle Bone Black(BBB)

Nobuhiro Iwamatsurequested to merge
iwamatsu/add-config-bbb into master

This adds configs and sources for Beagle Bone Black(BBB)

Signed-off-by: Nobuhiro Iwamatsu nobuhiro1.iwamatsu@toshiba.co.jp

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