gnu: Add u-boot, device-tree-compiler.

* gnu/packages/u-boot.scm (device-tree-compiler, u-boot): New variables.
---
 gnu/local.mk                                       |   4 +
 .../u-boot-device-tree-compiler-01_build_doc.patch |  21 ++++
 ...t-Add-missing-functions-to-shared-library.patch |  30 ++++++
 ...t-Add-some-missing-symbols-to-version.lds.patch |  33 ++++++
 gnu/packages/u-boot.scm                            | 114 +++++++++++++++++++++
 5 files changed, 202 insertions(+)
 create mode 100644 gnu/packages/patches/u-boot-device-tree-compiler-01_build_doc.patch
 create mode 100644 gnu/packages/patches/u-boot-device-tree-compiler-23-libfdt-Add-missing-functions-to-shared-library.patch
 create mode 100644 gnu/packages/patches/u-boot-device-tree-compiler-24_libfdt-Add-some-missing-symbols-to-version.lds.patch
 create mode 100644 gnu/packages/u-boot.scm