Add initial NuttX port for the original (white) BeagleBone board, which is
powered by the TI AM335x Sitara Cortex-A8 processor.
This commit includes:
- Board documentation
- Board support package files derived from BeagleBone black
- Architecture-specific page allocator for memory management in kernel build.
- Default configurations for both flat (`nsh`) and kernel (`knsh`) builds
running via U-Boot from a microSD card.
Signed-off-by: Lwazi Dube <lwazeh@gmail.com>