MAINTAINERS: fix address of IEEE 802.15.4 git tree

IEEE 802.15.4 git tree was moved from my private area to shared one.
Fix address accordingly.
Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -2863,7 +2863,7 @@ P:	Sergey Lapin
 M:	slapin@ossfans.org
 L:	linux-zigbee-devel@lists.sourceforge.net
 W:	http://apps.sourceforge.net/trac/linux-zigbee
-T:	git git://git.kernel.org/pub/scm/linux/kernel/git/lumag/lowpan.git
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/lowpan/lowpan.git
 S:	Maintained
 F:	net/ieee802154/
 F:	drivers/ieee801254/