MAINTAINERS: add entry for LICENSES and SPDX stuff

Thomas and I seem to have become the "unofficial" maintainers for these
files and questions about SPDX things.  So let's make it official.
Reported-by: "Darrick J. Wong" <darrick.wong@oracle.com>
Grumpily-acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Darrick J. Wong <darrick.wong@oracle.com>
Link: https://lore.kernel.org/r/20190827195310.GA30618@kroah.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

MAINTAINERS

@@ -9233,6 +9233,18 @@ F:	include/linux/nd.h
 F:	include/linux/libnvdimm.h
 F:	include/uapi/linux/ndctl.h
 
+LICENSES and SPDX stuff
+M:	Thomas Gleixner <tglx@linutronix.de>
+M:	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+L:	linux-spdx@vger.kernel.org
+S:	Maintained
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/spdx.git
+F:	COPYING
+F:	Documentation/process/license-rules.rst
+F:	LICENSES/
+F:	scripts/spdxcheck-test.sh
+F:	scripts/spdxcheck.py
+
 LIGHTNVM PLATFORM SUPPORT
 M:	Matias Bjorling <mb@lightnvm.io>
 W:	http://github/OpenChannelSSD