Create new fdt boardsetup command, fix bug parsing [] form of set values.

Previously ft_board_setup() was called by fdt_chosen() which was not
really correctly structured.  This splits ft_board_setup() out by creating
a new fdt boardsetup command.

Fix a bug when parsing fdt set command values which have the square
bracket form [00 11 22 33] - the length was updated incorrectly in when
parsing that form.

Signed-off-by: Gerald Van Baren <vanbaren@cideas.com>