MFC r283920, r283991, r283992, r284102:

r283920:
Add a configuration file to support the Cubox/Hummingboard SoC.

r283991:
Add initial support for building images for the Duovero Gumstix
board.

r283992:
Fix a whitespace nit.

r284102:
Set the correct UBLDR_LOADADDR for the Wandboard and
Cubox/Hummingboard images.

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