gnu: linux-libre: Update to 4.19.

gnu: linux-libre: Update to 4.19.

* gnu/packages/linux.scm (%linux-libre-version): Update to 4.19.
(%linux-libre-hash): Update hash.
(%linux-libre-4.18-patches): Rename to ...
(%linux-libre-4.19-patches): ... this, and remove a patch that is
no longer needed.
(linux-libre, linux-libre-arm-generic, linux-libre-arm-omap2plus):
Use %linux-libre-4.19-patches instead of %linux-libre-4.18-patches.
* gnu/packages/aux-files/linux-libre/4.18-arm.conf,
gnu/packages/aux-files/linux-libre/4.18-arm64.conf,
gnu/packages/aux-files/linux-libre/4.18-i686.conf,
gnu/packages/aux-files/linux-libre/4.18-x86_64.conf: Remove files.
* gnu/packages/aux-files/linux-libre/4.19-arm.conf,
gnu/packages/aux-files/linux-libre/4.19-arm64.conf,
gnu/packages/aux-files/linux-libre/4.19-i686.conf,
gnu/packages/aux-files/linux-libre/4.19-x86_64.conf: New files.
* Makefile.am (AUX_FILES): Adjust accordingly.