MAINTAINERS: add Andrew Morton for lib/*

Add myself as the fallthough maintainer for material under lib/.

Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

MAINTAINERS

@@ -12208,6 +12208,13 @@ F:	include/linux/nd.h
 F:	include/uapi/linux/ndctl.h
 F:	tools/testing/nvdimm/
 
+LIBRARY CODE
+M:	Andrew Morton <akpm@linux-foundation.org>
+L:	linux-kernel@vger.kernel.org
+S:	Supported
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-nonmm-unstable
+F:	lib/*
+
 LICENSES and SPDX stuff
 M:	Thomas Gleixner <tglx@linutronix.de>
 M:	Greg Kroah-Hartman <gregkh@linuxfoundation.org>