[dtc] Allow references to labels

[Jon Loeliger]

So, like, the other day David Gibson mumbled:
> dtc allows nodes to have labels, which at present are just re-emitted
> as symbols at the appropriate places when using asm-mode output.  It
> also allows "references" where the notation &/path/to/node in a cell
> list will be replaced with the phandle of the referenced node.
> 
> This patch extends the reference syntax to allow references to labels
> instead of just full device paths.  This allows nodes deep within the
> tree to be referenced with a shorter more convenient name.  References
> to labels are distinguished from reference to paths by the fact that
> paths must start with a /, but labels can never start with a /.
> 
> Signed-off-by: David Gibson <dwg at au1.ibm.com>
> 
> Index: dtc/livetree.c

Applied.

Thanks,
jdl