Add fdt_cells() to read scalar values encoded within a cell array,
reimplement fdt_u64() as a wrapper around this, and add fdt_u32() for
completeness.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Refactor device tree traversal to operate on the basis of describing
the token at a given offset, with no separate notion of a device tree
cursor.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
