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>
1 file changed