dtc: import latest upstream dtc

This updates scripts/dtc to commit 317a5d9 "dtc: zero out new label
objects" from git://git.jdl.com/software/dtc.git.

This adds features such as:
* /bits/ syntax for cell data.
* Math expressions within cell data.
* The ability to delete properties or nodes.
* Support for #line directives in the input file, which allows the use of
  cpp on *.dts.
* -i command-line option (/include/ path)
* -W/-E command-line options for error/warning control.
* Removal of spew to STDOUT containing the filename being compiled.
* Many additions to the libfdt API.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Jon Loeliger <jdl@jdl.com>
Signed-off-by: Rob Herring <rob.herring@calxeda.com>