This commit consolidates all BSP support files into the Buildroot standard
board/ directory. The concept of selectable boards in menuconfig remains
as-is but now lives in board/ instead.
Drop support for board-specific post-build.sh scripts, not needed atm. and
we should really use Buildroot _POST_INSTALL_HOOKS in the board .mk files
instead.
Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
