MAINTAINERS: add entry for UNIX sockets

Add a MAINTAINERS entry for UNIX socket, Kuniyuki has been
the de-facto maintainer of this code for a while.

Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250202014728.1005003-4-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

MAINTAINERS

@@ -16658,6 +16658,15 @@ F:	net/core/*sock*
 F:	net/core/scm.c
 F:	net/socket.c
 
+NETWORKING [UNIX SOCKETS]
+M:	Kuniyuki Iwashima <kuniyu@amazon.com>
+S:	Maintained
+F:	include/net/af_unix.h
+F:	include/net/netns/unix.h
+F:	include/uapi/linux/unix_diag.h
+F:	net/unix/
+F:	tools/testing/selftests/net/af_unix/
+
 NETXEN (1/10) GbE SUPPORT
 M:	Manish Chopra <manishc@marvell.com>
 M:	Rahul Verma <rahulv@marvell.com>