machine & kernel: Create new ANVL machine and add kernel source

Create a new "machine" for the ANVL board.
This requires that the kernel for the ANVL
board be added too.

Signed-off-by: Mark A. Greer <mgreer@animalcreek.com>
u-boot: Build the ANVL-specific u-boot code

Have the ANVL machine build the ANVL-specific
u-boot code.

Signed-off-by: Mark A. Greer <mgreer@animalcreek.com>