DTC 1.4.7

There have been a number of useful changes since v1.4.6:
  * Considerable improvements in libfdt's memory safety
  * Improved fdt_check_header() and new fdt_check_full() cuntions
  * Assorted bugfixes

So, here's another release.

dtc: Bump version to v1.4.7

We've accumulated a bunch of bugfixes, including considerable improvements
to libfdt's memory safety, so get ready for another release.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>